Composite electrodes with carrageenan for fuel cells

Abstract

The present technology relates generally to a fuel cell electrode including about 1 wt.% to about 10 wt.% carrageenan, about 0.5 wt.% to about 50 wt.% metal oxide having a dimension of about 0.1 nm to about 100 nm, and about 1 wt.% to about 20 wt.% of a catalyst comprising CeO2 and a metal catalyst. Fuel cell electrodes using carrageenan instead of NAFION® are more environmentally friendly and biodegradable. The fuel cell electrodes are useful for preparing direct ethanol fuel cells.

Description

COMPOSITE ELECTRODES WITH CARRAGEENAN FOR FUEL CELLSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 654,687, filed May 31, 2024, the entire contents of which is incorporated by reference herein in its entirety for any and all purposes.GOVERNMENT RIGHTS

[0002] This invention was made with government support under OIA- 1849243 awarded by The National Science Foundation, 80NSSC19M0236 awarded by The National Aeronautics and Space Administration, P120A210035 awarded by the Department of Education, and 1736093 awarded by the National Science Foundation. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present technology relates generally to fuel cell electrodes made with carrageenan and methods of making the same.SUMMARY

[0004] In an aspect, a fuel cell electrode is presented. The fuel cell electrode includes about 1 wt.% to about 10 wt.% carrageenan, about 0.5 wt.% to about 50 wt.% metal oxide having a dimension of about 0.1 nm to about 100 nm, and about 1 wt.% to about 20 wt.% of a catalyst comprising CeCh and a metal catalyst.

[0005] In any embodiment, the carrageenan may include a mixture of K-carrageenan and X- carrageenan. The carrageenan may include K-carrageenan. The fuel cell may include about 1 wt.% to about 5 wt.% carrageenan. The metal oxide may include TiCh, CeCh, ZrCh, or a mixture of two or more thereof. The metal oxide may include nanoparticles. The metal oxide may include TiCh nanoparticles, TiCh nanorods, TiCh nanotubes, TiCh nanofibers, or a mixture of two or more thereof. The metal oxide may include TiCh nanoparticles. The fuel cell electrode may include about 1 wt.% to about 10 wt.% metal oxide. The fuel cell electrode may include about 5 wt.% metal oxide. The metal catalyst may include nickel, copper, cobalt, iron, ruthenium, rhodium, palladium, platinum, silver, or a mixture of two ormore thereof. The metal catalyst may include nickel disposed on a surface of CeCh particles in a ratio of Ni to CeCh of about 1 :9. The fuel cell electrode may include about 5 wt.% to about 15 wt.% metal catalyst. The fuel cell electrode may include about 10 wt.% metal catalyst. The fuel cell electrode may include about 1 wt.% to about 10 wt.% sulfonated tetrafluoroethylene based fluoropolymer-copolymer. The fuel cell electrode may have an ionic conductivity at about 20 °C of 10'4S / cm or greater. The fuel cell electrode may produce a current density for the electrooxidation of ethanol in an electrolyte of 1 M ethanol and 1 M KOH of 9 mA / cm2or greater.

[0006] In another aspect, a method of forming the fuel cell electrode disclosed herein is presented. The method includes forming an aqueous solution of carrageenan with the metal oxide and the catalyst dispersed therein, and forming the fuel cell electrode by casting and drying the aqueous solution.

[0007] In another aspect, a fuel cell includes the fuel cell electrode disclosed herein, a counter electrode, and a polymer electrolyte membrane disposed between the fuel cell electrode and the counter electrode. The fuel cell may be a direct ethanol fuel cell.

[0008] Further aspects and embodiments of the present technology are described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is an graph of a differential scanning calorimetry (DSC) thermograms showing the thermal stability of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiO2 nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiO2 NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiO2 NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiO2NPs.

[0010] FIG. 2 is a graph of X-ray diffraction (XRD) measurements of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiO2NPs.

[0011] FIG. 3A is a graph of Fourier-transform infrared (FT-IR) spectra in the range of 4000 cm’1to 400 cm’1of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiO2NPs.

[0012] FIG. 3B is a graph of Fourier-transform infrared (FT-IR) spectra in the fingerprint region of 1400 cm’1to 400 cm’1of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiO2NPs.

[0013] FIG. 4A shows scanning electron microscopy (SEM) images of carrageenan at different magnifications.

[0014] FIG. 4B shows SEM images of carrageenan with TiCh NPs at a concentration of 0.1 wt.% (CR0.1%) at different magnifications.

[0015] FIGS. 5A-5D show SEM images of carrageenan with different concentrations of TiCh NPs as compared to TiCh NPs alone. FIG. 5A is an SEM image of carrageenan with TiCh NPs at a concentration of 0.5 wt.%. FIG. 5B is an SEM image of carrageenan with TiCh NPs at a concentration of 1 wt.%. FIG. 5C is an SEM image of carrageenan with TiCh NPs at a concentration of 5 wt.%. FIG. 5D is an SEM image of TiCh NPs alone.

[0016] FIGS. 6 A and 6B are cyclic voltammograms (CVs) in an aqueous electrolyte solution of 1 M KOH at a scan rate of 100 mV / s. FIG. 6A is a CV of glassy carbon electrode (GCE), CR, CR5%, and CR5% with Ni / CeO2(10 wt.% Ni). FIG. 6B is a CV of GCE, NAFION®, and NAFION® with Ni / CeO2(10 wt.% Ni).

[0017] FIGS. 7A and 7B are CVs in an electrolyte solution of 1 M KOH and 1 M ethanol at a scan rate of 100 mV / s. FIG. 7A is a CV of glassy carbon electrode (GCE), CR, CR5%, and CR5% with Ni / CeO2(10 wt.% Ni). FIG. 7B is a CV of GCE, NAFION®, and NAFION® with Ni / CeO2(10 wt.% Ni).

[0018] FIG. 8 is a CV of CR5% with Ni / CeCh (10 wt.% Ni) and NAFION® with Ni / CeCh (10 wt.% Ni) in a solution of 1 M KOH and 1 M ethanol at 100 mV / s.

[0019] FIGS. 9A and 9B are CVs of CR5% with Ni / CeO2(10 wt.% Ni) (FIG. 9A) and NAFION® with Ni / CeO210 wt.% Ni (FIG. 9B) at different scan rates from 10 mV / s to 100 mV / s in a solution of 1 M KOH and 1 M ethanol.

[0020] FIGS. 10A and 10B are graphs of current vs. square root of scan rate for CR5% with Ni / CeO2(10 wt.% Ni) (FIG. 10A) and NAFION®with Ni / CeO210 wt.% Ni (FIG. 10B).

[0021] FIGS. 11 A and 1 IB are CVs of CR5% with Ni / CeO2(10 wt.% Ni) (FIG. 11 A) and NAFION® with Ni / CeO210 wt.% Ni (FIG. 1 IB) at 20, 40, and 60 cycles at a scan rate of 50 mV / s in a solution of 1 M KOH and 1 M ethanol.

[0022] FIG. 12 is a graph of energy dispersive X-ray spectroscopy (EDS) spectra of carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiO2nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiO2NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiO2NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiO2NPs (CR5%).

[0023] FIGS. 13 A and 13B are CVs comparing CR5% with Ni / CeO2to CR5% with CeO2, y-AhCh, and Ni / y-AkCh (FIG. 13 A) and comparing NAFION® with Ni / CeO2to NAFION® with CeO2, y-Al2O3, and Ni / y-AhOs (FIG. 13B).DETAILED DESCRIPTION

[0024] It is to be appreciated that certain aspects, modes, embodiments, variations, and features of the present methods are described below in various levels of detail in order to provide a substantial understanding of the present technology.Definitions

[0025] Unless defined otherwise, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs.

[0026] As used herein and in the appended claims, singular articles such as “a” and “an” and “the” and similar referents in the context of describing the elements (especially in thecontext of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential. For example, reference to “a cell” includes a combination of two or more cells, and the like. Generally, the nomenclature used herein and the laboratory procedures in cell culture, molecular genetics, organic chemistry, analytical chemistry and nucleic acid chemistry and hybridization described below are those well- known and commonly employed in the art.

[0027] As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term - for example, “about 10 wt.%” would be understood to mean “9 wt.% to 11 wt.%.” It is to be understood that when “about” precedes a term, the term is to be construed as disclosing “about” the term as well as the term without modification by “about” - for example, “about 10 wt.%” discloses “9 wt.% to 11 wt.%” as well as disclosing “10 wt.%.”

[0028] The phrase “and / or” as used in the present disclosure will be understood to mean any one of the recited members individually or a combination of any two or more thereof - for example, “A, B, and / or C” would mean “A, B, C, A and B, A and C, B and C, or the combination of A, B, and C.”

[0029] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, eachrange discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 atoms refers to groups having 1, 2, or 3 atoms. Similarly, a group having 1-5 atoms refers to groups having 1, 2, 3, 4, or 5 atoms, and so forth.The Present Technology

[0030] Synthetic polymers, such as polyfluorinated sulfonic acid ionomers (for example, NAFION®), are conventionally widely used in the manufacture of direct ethanol fuel cell electrodes. However, NAFION® has the drawbacks of elevated price, processibility issues stemming from its nature as a perfluorinated polymer, and its adverse effects on human health and the environment. Thus, there is great interest in developing direct alcohol fuel cell electrodes that are more environmentally friendly and biodegradable.

[0031] Disclosed herein are fuel cell electrodes that include carrageenan, a metal oxide, and a catalyst. The fuel cell electrodes may be used in direct ethanol fuel cells in which ethanol is fed directly into the fuel cell as fuel to produce electricity via the oxidation of ethanol to form carbon dioxide. The fuel cell electrode disclosed herein may be an anode, where the ethanol oxidation occurs on the catalyst of the fuel cell electrode according to the following reaction:C2H5OH + 3 H2O 12 H++ 12 e + 2 CO2.At the cathode, oxygen reduction may occur according to the following reaction:3 O2 + 12 H + l 2 e 6 H2O.Electrons may be transported through an external circuit from anode to cathode, providing power to connected devices.

[0032] The fuel cell electrode may include K-carrageenan or a mixture of K-carrageenan and k-carrageenan. Carrageenan is a sulfated linear polysaccharide that may be derived from a red seaweed belonging to the class Rhodophyceae . The K-carrageenan may have a structure according to Formula IFormula IThe X-carrageenan may have a structure according to Formula IIFormula IIThe fuel cell electrode may include about 1 wt.% to about 10 wt.% carrageenan. For example, the fuel cell may include carrageenan in an amount of about 1 wt.% to about 9 wt.%, about 1 wt.% to about 8 wt.%, about 1 wt.% to about 7 wt.%, about 1 wt.% to about 6 wt.%, or about 1 wt.% to about 5 wt.%. The fuel cell may include about 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, or any value therebetween.

[0033] The metal oxide in the fuel cell electrode may have the form of a nanomaterial having a dimension of about 0.1 nm to about 100 nm. The nanoparticles may be nanoparticles, nanorods, nanotubes, nanofibers, or a mixture of two or more thereof. The nanoparticles may have a dimension (e.g., a diameter in the case of nanoparticles) of about 1 nm to about 80 nm, about 1 nm to about 60 nm, about 10 nm to about 50 nm, or about 15 nm to about 30 nm. The nanoparticles may have a diameter of about 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value therebetween. The metal oxide may include TiCh, CeCh, ZrCh, or a mixture of two or more thereof. For example, the metal oxide may include TiCh in the form of nanorods, nanotubes, nanofibers, or a mixture of two or more thereof. The metal oxide may be present in the fuel cell electrode in an amount of about 0.5 wt.% to about 50 wt.%. For example, the metal oxide may be present in the fuel cell electrode in an amount of about 1 wt.% to about 40 wt.%, about 1 wt.% to about 30 wt.%, about 1 wt.% to about 20 wt.%, about 1 wt.% to about 10 wt.%, or about 1 wt.% to about 5 wt.%. For example, the metal oxide may be present in the fuel cell electrode in anamount of about 0.1 wt.%, 0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 10 wt.%, or any value therebetween.The catalyst may include a metal oxide support and a metal catalyst on the metal oxide support. The metal oxide support may include TiCh, CeCh, ZrCh, or a mixture of two or more thereof. The metal catalyst may include nickel, copper, cobalt, iron, ruthenium, rhodium, palladium, platinum, silver, or a mixture of two or more thereof. For example, the metal catalyst may include a metal oxide support including CeCh and a metal catalyst including nickel. The catalyst may be present in the fuel cell electrode in an amount of about 1 wt.% to about 20 wt.%. The catalyst may be present in the fuel cell electrode in an amount of about 1 wt.%, about 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, 11 wt.%, 12 wt.%, 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.%, or any value therebetween. The metal catalyst may be present in the fuel cell electrode in an amount of about 1 wt.% to about 20 wt.%, about 5 wt.% to about 15 wt.%, about 8 wt.% to about 12 wt.%, or about 10 wt.%. The ratio of metal catalyst to metal oxide support may be about 1 :20 to about 1 : 1, such as about 1 :20, about 1 : 19, about 1 : 18, about 1 : 17, about 1 : 16, about 1 : 15, about 1 : 14, about 1 : 13, about 1 :12, about 1 : 11, about 1 : 10, about 1 :9, about 1 :8, about 1 :7, about 1 :6, about 1 :5, about 1 :4, about 1 :3, about 1 :2; or about 1 : 1. For example, the ratio of metal catalyst to metal oxide support may be about 1 :9.

[0034] In any embodiment, the fuel cell electrode may further include a sodium salt, a potassium salt, or a combination thereof. The sodium salt may be a sodium halide, such as NaF, NaCl, NaBr, or Nal. The potassium salt may be a potassium halide, such as KF, KC1, KBr, or KI. The sodium salt, a potassium salt, or a combination thereof may be present in the fuel cell electrode in an amount of about 0 wt.% to about 5 wt.%.

[0035] In any embodiment, the fuel cell electrode may further include a sulfonated tetrafluoroethylene based fluoropolymer-copolymer additive. For example, the sulfonated tetrafluoroethylene based fluoropolymer-copolymer additive may include NAFION®. The sulfonated tetrafluoroethylene based fluoropolymer-copolymer additive may be present in the fuel cell electrode in an amount of about 0.1 wt.% to about 20 wt.% or about 1 wt.% to about 10 wt.%. For example, the fuel cell electrode may include 1 wt.%, 2 wt.%, 3 wt.%, 4 wt.%, 5 wt.%, 6 wt.%, 7 wt.%, 8 wt.%, 9 wt.%, 10 wt.%, or any value therebetween.

[0036] The fuel cell electrode may have an ionic conductivity at about 20 °C to about 30 °C of about 10'5S / cm or greater, about 10'4S / cm or greater, or about 10'3S / cm or greater. The fuel cell electrode may be used in a direct ethanol fuel cell to produce a current density from the electrooxidation of ethanol in an electrolyte of 1 M ethanol and 1 M KOH of about 5 mA / cm2or greater, about 6 mA / cm2or greater, about 7 mA / cm2or greater, about 8 mA / cm2or greater, about 9 mA / cm2or greater, or about 10 mA / cm2or greater.

[0037] In another aspect, a method of forming the fuel cell electrode disclosed herein is presented. The method may include forming an aqueous solution of carrageenan with the metal oxide and the catalyst dispersed therein, and casting and drying the aqueous solution to form the fuel cell electrode.The aqueous solution may be prepared by first preparing a carrageenan solution in water (e.g., distilled water) at a concentration of about 1 wt.% to about 10 wt.% with a base (e.g., sodium hydroxide or potassium hydroxide) added to a concentration of about 1 mM to about 5 mM (e.g., 1 mM, 2 mM, 3 mM, 4 mM, or 5 mM). The carrageenan solution may be mixed (e.g., by hand, by disperser, by mixer, or by stir bar) until substantially homogeneous or homogeneous. In a separate vessel, the metal oxide nanomaterial may be dispersed in water (e.g., at a concentration of about 0.1 wt.% to about 10 wt.%). In a separate vessel, the catalyst may be dispersed in water, methanol, or ethanol in a concentration of about 1 mg / mL, 2 mg / mL, or 3 mg / mL. Then an amount of the carrageenan solution and an amount of the catalyst solution may be added to the dispersed metal oxide nanomaterial and mixed until substantially homogeneous or homogeneous. The mixture may be cured in a predetermined shape at a temperature of about 50 °C to about 100 °C (e.g., about 65 °C) for about 2 hours to about 48 hours (e.g., about 24 hours).

[0038] In another aspect, a fuel cell includes the fuel cell electrode disclosed herein, a counter electrode, and a polymer electrolyte membrane disposed between the fuel cell electrode and the counter electrode. The fuel cell may be a direct ethanol fuel cell. The polymer electrolyte membrane may include a polymer such as polyfluorinated sulfonic acid ionomers (for example, NATION®), polyvinyl alcohols, polybenzimidazoles, chitosans, sodium alginates, any other suitable polymers for fuel cell polymer electrolyte membranes, or combinations of any two or more thereof. The polymer electrolyte membrane may not include carrageenan.EXAMPLES

[0039] The present technology is further illustrated by the following Examples, which should not be construed as limiting in any way. The examples herein are provided to illustrate advantages of the present technology and to further assist a person of ordinary skill in the art with preparing or using the compositions and systems of the present technology. The examples should in no way be construed as limiting the scope of the present technology, as defined by the appended claims. The examples can include or incorporate any of the variations, aspects, or embodiments of the present technology described above. The variations, aspects, or embodiments described above may also further each include or incorporate the variations of any or all other variations, aspects, or embodiments of the present technology. The following Examples demonstrate the preparation, characterization, and use of illustrative fuel cell electrodes. In these examples, the carrageenan nanocomposite membranes (mixture of K- carrageenan and k-carrageenan) with different concentrations of titanium dioxide nanoparticles (TiCh NPs) and Ni / CeCh (10 wt. % Ni) were fabricated and investigated as fuel cell electrodes for the oxidation of ethanol.Example 1: Synthesis and Characterization of Carrageenan Nanocomposites

[0040] To develop more environmentally-friendly and biodegradable fuel cell electrodes for direct ethanol fuel cells, a detailed analysis of the thermal, electrical, and structural properties of membranes made of carrageenan nanocomposites useful as fuel cell electrodes was conducted. The carrageenan nanocomposites include K-carrageenan and k-carrageenan biopolymer with TiCh NPs and Ni / CeCh catalyst incorporated therein.Materials

[0041] Titanium dioxide (TiCh) nanoparticles (TiCh NPs) with a purity of 99.5 wt.% and particle size of approximately 21 nm; mixed carrageenan (K and X); ethanol (99.5 % v / v); sodium hydroxide (NaOH 99.99 % v / v); potassium hydroxide (KOH, 99.99 % v / v); NAFION® perfluorinated resin solution 5 wt.% in lower aliphatic alcohols water mix were used. Reagents were used without modification and purchased from Sigma Aldrich. Glassy carbon (GC) electrodes (3.0 mm diameter) from Bio- Analytical Systems were used as working electrodes. The deionized water used for the experiments was previously distilled and pumped through a Nanopure system (Barnstead) to give a resistivity of 18.2 MQcm.Synthesis of Carrageenan Nanocomposites

[0042] The procedure to prepare the carrageenan nanocomposites with TiCh NPs was as follows. A polysaccharide solution of 4.7 wt. % was prepared by mixing 5 ± 0.01 g of carrageenan and 100 mL of distilled water. Then 1 mL of sodium hydroxide solution (NaOH) at 0.25 M was added and dispersed (an T 18 B SI ULTRA-TURRAX disperser was used, with an output power of 40% to homogenize the mixture) to form the 4.7 wt.% carrageenan solution. Subsequently, in different beakers, with a volume of 25 mL of distilled water, the TiCh NPs were dispersed with a concentration of 0.1 wt. %, 0.5 wt. %, 1 wt. %, and 5 wt. % and stirred for 5 minutes with an output power of 16.0 %. To these samples of dispersed TiCh NPs, 15 ± 0.01 g of 4.7 wt. % carrageenan solution was added and stirred for 5 minutes with an output power of 40 %. Then the mixture was placed into Petri dishes at cured at 65° C for 24 hours.

[0043] The procedure to prepare the carrageenan nanocomposites with TiCh NPs and Ni / CeCh catalyst was as follows. Ni / CeCh (10 wt. % Ni) catalyst was prepared by incipient wetness impregnation of an aqueous solution of nickel (II) nitrate hexahydrate (Alfa-Aesar, 98 %) on cerium oxide (Daiichi Kigenso Kagaku Kogyo Co., LTD). The obtained powder was dried overnight at 120 °C, followed by calcination at 400 °C for 3 hours at a ramp rate of 5 °C / min under flowing dried air at 40 mL / min. A polysaccharide solution of 4.7 wt. % was prepared by mixing 5 ± 0.01 g of carrageenan and 100 mL of distilled water. Then 1 mL of sodium hydroxide solution (NaOH) at 0.25 M was added and dispersed with an output power of 40% to homogenize the mixture and form the 4.7 wt.% carrageenan solution.Subsequently, in different beakers, with a volume of 25 mL of distilled water, the TiO2 NPs were dispersed with a concentration of 0.1 wt. %, 0.5 wt. %, 1 wt. %, and 5 wt. % and stirred for 5 minutes with an output power of 16.0 %. To these samples of dispersed TiCh NPs, 15 ± 0.01 g of 4.7 wt. % carrageenan solution was added and stirred for 5 minutes with an output power of 40 %. 5 mg Ni / CeCh (10 wt. % Ni) was dispersed in 2.5 mL ethanol and 80 pL of 4.7 wt.% carrageenan solution with 5 wt. % TiCh NPs was added. The resulting solution was sonicated for 30 minutes. 5 pL of the resulting solution was placed on the surface of a glass carbon and air dried for 30 minutes at room temperature (about 20 °C to about 22 °C) to form the electrode.Differential Scanning Calorimetry (DSC)

[0044] To study the thermal stability of the samples, a Mettler Toledo DSC 822e calorimeter was used. Nanocomposites of approximately 6 ± 1 mg were tested in aluminum capsules with dry nitrogen used as a purge gas, with a flow rate of 60 mL / min and a heating rate of 5 °C / min from room temperature to 500 °C.X-ray Diffraction (XRD)

[0045] The crystalline structures of the samples were studied using a Rigaku X-ray diffractometer (Smartlab) with a Cu-Kcr monochromatic radiation source. Data was collected from 20 to 80 degrees with a sampling step of 0.02 degrees and a scanning speed of 1 degree / min.Fourier Transform Infrared Spectroscopy (FTIR)

[0046] Fourier transform infrared spectroscopy measurements (FTIR) were recorded by a Shimadzu IRAffinity-lS spectrophotometer coupled with an attenuated total reflectance cell (ATR). The measurements were carried out in a range of 400 to 4000 cm'1with 100 scans and a resolution of 2 cm'1.Impedance Spectroscopy (IS)

[0047] The electrical measurements of the nanocomposites were made with the help of the HIOKI 3522-50 L.C.R. impedance analyzer (Hioki E. E. Corporation, Melrose, MA, USA) in the frequency range of 42 MHz to 5 MHz at room temperature.Scanning Electron Microscopy (SEM)

[0048] Surface morphology was examined using a scanning electron microscope (SEM). The micrographs were captured on a JSM-6360 (JEOL, Japan) with an acceleration voltage of 8 kV and a working distance of 8 mm. The observation was conducted at room temperature.Cyclic Voltammetry Measurements (CV)

[0049] For electrochemical characterization, cyclic voltammetry was used through a PalmSens4 potentiostat with a traditional three-electrode cell composed of a glassy carbon working electrode (GCE), a platinum wire as an auxiliary electrode, and an Ag / AgCl as a reference electrode. The GCE was coated with different composites: 4.7 wt.% carrageenansolution (CR), 4.7 wt.% carrageenan solution with 5 wt.% TiCh (CR5%), and 4.7 wt.% carrageenan solution with 5 wt.% TiCh and NiCeCh at 10 wt.% Ni (CR5% + Ni / CeCh at 10 wt. % Ni) and different NAFION® composites: NAFION®, and NAFION®+ Ni / CeCh (10 wt. % Ni) solutions. The measurements were taken at room temperature in electrolyte solutions of 10 mL 1 M KOH or 10 mL 1 M KOH with 1 M ethanol at a scan rate of 100 mV / s in a range of -1.4 V to 1.4 V.Characterization of Carrageenan Nanocomposite Electrodes

[0050] The procedure used to prepare the glassy carbon (G.C.) working electrodes was as follows. The bare G.C. electrode was analyzed. To prepare the carrageenan-coated G.C. electrode, the surface of the G.C. electrode was polished with 5 pm alumina and washed several times with ultrapure water before 5 pL of carrageenan solution (5 mg in 10 ml of ultrapure water) was disposed on the G.C. electrode and dried for 30 minutes. To prepare the carrageenan / TiCh nanocomposite electrode, 4.7 wt.% carrageenan solution with 5 wt.% TiCh (CR5%) was disposed on the G.C. electrode and dried for 30 minutes. To prepare the carrageenan / TiCh / CeCh / Ni composite electrode, 5 mg of Ni / CeCh (10 wt. % Ni) was mixed with 2.5 mL of ethanol and 80 pl CR5% solution and sonicated for 30 min. An analogous procedure was used to prepare the NAFION® membranes, using NAFION® in place of carrageenan. Measurements were made in a 1 M KOH electrolyte solution or 1 M KOH with 1 M ethanol solution at a scan rate of 100 mV / s over a range of -1.4 V to 1.4 V.Assembly of Working Electrode with CR5% and NAFION in the Modification of Glassy Carbon (GC) Electrodes

[0051] For the first electrode, we mixed 5 mg Ni / CeO2 (10 wt. % Ni) with 2.5 mL ethanol and 80 pL CR5% solution (5 mg in 10 mL ultrapure water) and sonicated for 30 minutes. On the surface of the working electrode, 5 pL of CR5% + Ni / CeO2 (10 wt. % Ni) solution was placed and air dried for 30 minutes at room temperature. For the second electrode, the procedure was similar, but this time 80 pL of NAFION® solution was used instead of the CR5% solution over a range of 0.2 V to 0.8 V.Energy dispersive X-ray spectroscopy (EDX)

[0052] Energy dispersive X-ray spectroscopy measurements were conducted in a scanning electron microscope (SEM). The spectra were taken on a JSMIT-500 HR (JEOL, Japan),with an accelerating voltage of 20 kV and a working distance of 10 mm. All spectra were taken at room temperature (about 20 °C to about 22 °C).Example 2: Thermal Stability of Nanocomposites

[0053] The thermal stability of the materials was characterized to determine operating temperatures. FIG. 1 is an graph of a differential scanning calorimetry (DSC) thermograms showing the thermal stability of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiCh NPs. Two thermal peaks were observed in the carrageenan and the four composites (CR0.1%, CR0.5%, CR1%, and CR5%). The first peak corresponded to an endothermic peak observed around 100 °C, which may correspond to water physically bound in the composites and carrageenan. A second peak was observed around 200 °C, which corresponded to an exothermic peak. The second peak may be associated with a crystalline phase or decomposition process in the different composites. A shift of the exothermic peak was observed towards lower temperatures as the concentration of TiCh particles increased. This shift may reflect a change in the thermal properties of the carrageenan, possibly due to structural changes of the nanocomposites. TiCh NPs alone did not present any thermal peaks due to their thermal stability over a wide range of temperatures. To investigate the possibility of structural change in the nanocomposites due to the variation of TiCh NPs, X-ray diffraction measurements were analyzed.Example 3: Structural Characterization of the Samples

[0054] The X-ray diffraction (XRD) measurements were collected. FIG. 2 is a graph of X- ray diffraction (XRD) measurements of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiCh NPs. Diffractograms showed a crystalline phase in the mixed carrageenan sample belonging to an inorganic salt, which may correspond to sylvite potassium chloride (KC1) or halite sodium chloride (NaCl) impurity in the carrageenan, or may correspond to cohesive properties in carrageenan polysaccharides. The appearance of the peaks maycorrespond to the nanoparticle phase of TiCh observed from the concentration of 0.1 wt. %, together with the phases of the inorganic salts belonging to the mixed carrageenan. These two phases may be maintained until the nanocomposite 5 wt. %, where the phases of the salts disappeared by complement, while the phase of TiCh prevailed completely. This behavior is consistent with an increase in the concentration of TiCh nanoparticles. This phase of TiCh was in accordance with the card number (00-021-1276) of the JCPDF. This change in the intensity of the peaks indicated a concentration change in the samples due to the variation of TiCh, which may indicate a change in the thermal properties observed in the DSC measurements. This structural and thermal change of the samples also may imply possible changes occur in the different bonds in the nanocomposites. Therefore, infrared spectroscopy measurements were conducted for the mixed carrageenan, TiCh NPs, and the different nanocomposites.Example 4: Structural Characterization of the Samples

[0055] The oscillation modes (vibrations) of the carrageenan structure and the TiCh NPs were characterized. FIG. 3A is a graph of Fourier-transform infrared (FT-IR) spectra in the range of 4000 cm'1to 400 cm'1of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiCh NPs. FIG. 3B is a graph of Fourier-transform infrared (FT-IR) spectra in the fingerprint region of 1400 cm'1to 400 cm'1of the nanocomposites: carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiCh nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiCh NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiCh NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiCh NPs (CR5%), and TiCh NPs. Carrageenan contributions were observed in the bands corresponding to both K-carrageenan and k-carrageenan, together with the common bands for both, showing more intense for one type of carrageenan than for the other. In FIG. 3 A, the spectrum showed a band at 3392 cm'1and 3412 cm'1that corresponded to the OH stretch vibrations, while the band at 1641 cm'1corresponded to the water bound at the nanocomposites and at the TiO2 NPs. The region to identify the different carrageenan types was the region of the fingerprint, which corresponded to the spectrum between 1500 and 400 cm'1(Fig. 3B), where a band was observed at 1026 cm'1characteristic of the X -carrageenan,while the bands at 844 cm'1and 731 cm'1corresponded to the K-carrageenan. The peak at 1222 cm'1corresponded to O=S=O (asymmetric stretch) and was shown as a broad peak due to the contribution of these groups by the two carrageenan types (K and X). For its part, another characteristic band was the 925 cm'1that belonged to the coupling of the stretching vibrations of the C-O-C in the 3,6-anhydrous-D-galactose (3,6-anhydrogalactose). In this same region of the fingerprint, there was a very particular behavior in the bands since there was a progressive decrease in its intensity as the percentage of nanoparticles of TiCh increased (0.1 wt. %, 0.5 wt. %, and 1 wt. %) and a reduction in the intensity of the bands for the sample of 5 wt. %, possibly due to the interaction of TiCh with the external groups in the mixed carrageenan such as the glycosidic bonds in 1002 cm'1, the vibrations of stretches of the C-O-C in 3,6-anhydrogalactose in 925 cm'1, groups C4-O-S in galactose (stretch) in 844 cm'1, groups C4-O-S in galactose (stretch) in 700 cm'1and the groups O=S=O (doubling) in 601 and 560 cm'1. These last two bands did not show significant changes, which may correspond with the bands belonging to the vibrations of the Ti-0 groups. Table 1 shows a comparison of K-carrageenan and k-carrageenan peaks in the FT-IR spectra.Table 1. Bands and functional groups detected in nanocomposites samples corresponding to K and X carrageenan (+, present; absent).Example 5: Electrical Properties of the Samples

[0056] Electrical behavior of the nanocomposites was investigated using Cole-Cole plots. The ionic conductivity values at room temperature (about 20 °C) are shown in Table 2. The ionic conductivity at room temperature was estimated from the following equation:where t is the thickness of the nanocomposite, Rb is the electrical resistance of the package, and A is the contact area of the electrodes. The ionic conductivity value for carrageenan (CR) was 1.07 x 10'4S / cm, two orders of magnitude greater than previously reported. Without being bound by any theory, this increase in conductivity may be due to traces of inorganic salts (KC1 and NaCl), observed in X-ray measurements, which may facilitate ion conduction. The conductivity results indicated an increase in conductivity as the concentration of TiCh nanoparticles increased, with higher conductivity the CR5% nanocomposite of 2.08 x 10'4S / cm. Without being bound by any theory, the addition of TiCh nanoparticles may facilitate the movement of hydrogen protons through the polymer chains, which may improve the conductivity of the nanocomposites. However, there are variations in the conductivity values that may be attributed to the interaction of Ti+with OH groups of carrageenan as were observe in the FTIR measurements. Without being bound by any theory, the decrease in conductivity values for higher concentrations of TiO2 may be attributed to the formation of clusters in the samples, as seen in the SEM images, which may make it difficult for the ions to pass through the bulk of nanocomposites.Table 2. Conductivity values of nanocomposites.Dielectric constants of the nanocomposites were characterized. There was an increase in the dielectric constant value at low frequencies, and the dielectric loss decreased for higher frequencies until reaching a constant value. In addition, with the increase in the concentration of TiCh nanoparticles, there was an increase in the values of the dielectric constant and the dielectric loss until they reached a higher value for the CR5% sample, which was in accordance with the conductivity results. Without being bound by any theory, this increase may be due to the polarization effect of the dipoles, ions, and charge space in the samples close to the electrodes. At high frequencies, the dipoles and ions may not follow the frequency of the applied electric field, which may reduce the charge accumulation in the electrode / electrolyte interface, causing the dielectric constant and the dielectric loss to decrease suddenly. The values of the dielectric constant for nanocomposites indicate that they are good candidates for use in capacitors and fuel cells.Example 6: Morphology of Nanocomposites

[0057] FIG. 4A shows scanning electron microscopy (SEM) images of carrageenan at different magnifications. 410 shows a low magnification SEM micrograph of the surface of carrageenan (CR). The area enclosed by the red circle had an amorphous surface, typical of carrageenan, as shown in 412, while in 414, the area enclosed by the black circle presented cube-shaped agglomerates, which correspond to the inorganic salts KC1 and NaCl, evidenced by the results of X-rays. In comparison, FIG. 4B shows SEM images of carrageenan with TiCh NPs at a concentration of 0.1 wt.% (CR0.1%) at different magnifications. 416 shows the surface of carrageenan with a concentration of 0.1% of TiO2 NPs (CR0.1%). The area enclosed by the blue circle had micro clusters embedded in the surface belonging to the TiCh NPs, as shown in 418. In addition 419 shows the formation of large islands corresponding to the cube-shaped structure of inorganic salts.

[0058] FIGS. 5A-5D show SEM images of carrageenan with different concentrations of TiCh NPs (0.5, 1, and 5%) as compared to TiCh NPs alone. FIG. 5 A is an SEM image of carrageenan with TiCh NPs at a concentration of 0.5 wt.%. FIG. 5B is an SEM image of carrageenan with TiCh NPs at a concentration of 1 wt.%. FIG. 5C is an SEM image of carrageenan with TiCh NPs at a concentration of 5 wt.%. FIG. 5D is an SEM image of TiCh NPs alone. Comparing the CR0.5% sample (FIG. 5 A) with the CR (FIG. 4A) and CR0.1% (FIG. 4B) samples, the surface area covered by the large islands of cube-shaped structures decreased. The structures were limited to isolated islands. In contrast, the number of micro clusters increased compared to FIG. 4B. FIG. 5B corresponds to carrageenan with a concentration of 1% of TiCh NPs (CR1%), in comparison, with samples CR, CR0.1%, and CR0.5%, cube structures were not observed, but an amorphous area, where the agglomeration of micro TiCh NPs clusters was observed. FIG. 5C shows the nanocomposite with the higher concentration of TiCh NPs, 5% (CR5%), where the surface was almost completely covered by a continuous film of TiCh NPs. No structured cubes were observed, and the micro clusters were limited to the smallest points. These results were in agreement with the X-ray measurements, where a progressive increase in the TiCh peaks was observed with a decrease in the phase corresponding to the inorganic salts (KC1 and NaCl). On the other hand, FIG. 5D showed pure TiO2 NPs, where the micro-clusters were observed.Example 7: Cyclic Voltammetry (CV) Measurements

[0059] FIGS. 6 A and 6B are cyclic voltammograms (CVs) in an aqueous electrolyte solution of 1 M KOH at a scan rate of 100 mV / s in a range of -1.4 V to 1.4 V. FIG. 6A is a CV of the glassy carbon electrode (GCE) used as substrate for the nanocomposites, CR, CR5%, and CR5% with Ni / CeO2(10 wt.% Ni). FIG. 6B is a CV of GCE, NAFION®, and NAFION®with Ni / CeO2(10 wt.% Ni). These measurements showed small reduction peaks for the GCE and the CR5% membrane mixed with Ni / CeO2(10 wt.% Ni) (Fig. 6A). Similarly, measurements showed small reduction peaks for the FCE and the NAFION®with Ni / CeO2(10 wt.% Ni) (Fig. 6B).Example 8: Ethanol Oxidation

[0060] FIGS. 7 A and 7B are CVs in an electrolyte solution of 1 M KOH and 1 M ethanol at a scan rate of 100 mV / s over a range of -1.4 V to 1.4 V. FIG. 7A is a CV of glassy carbon electrode (GCE), CR, CR5%, and CR5% with Ni / CeO2(10 wt.% Ni). FIG. 7B is a CV ofGCE, NAFION®, and NAFION® with Ni / CeCh (10 wt.% Ni). The performance of the membranes in alkaline medium (KOH) was evaluated for ethanol oxidation using cyclic voltammetry measurements. FIG. 7A showed two current density peaks corresponding to the oxidation of ethanol around 0.35 V and one reduction peak around -0.35 V for the CR5% membrane mixed with Ni / CeO2. Similarly, Fig. 7B showed two small oxidation peaks around 0.35 V and one reduction peak around -0.35 V for the NAFION® membrane mixed with Ni / CeO2. These voltammograms showed the similarity between the CR5% membrane, NAFION® and Ni / CeO2 in oxidizing ethanol. However, the current density peaks were greater with the CR5% membrane than with the NAFION® membrane.

[0061] FIG. 8 is a CV of CR5% with Ni / CeO2(10 wt.% Ni) and NAFION® with Ni / CeO2(10 wt.% Ni) in a solution of 1 M KOH and 1 M ethanol at 100 mV / s. Measurements were conducted in the voltage range between 0.2 V and 0.8 V, which included the two oxidation peaks by the membranes. The cyclic voltammograms of the membranes were compared for CR5% + Ni / CeO2 (10 wt. % Ni) and NAFION® + Ni / CeO2 (10 wt. % Ni) in a solution of 1 M KOH and 1 M ethanol at a scan rate of 100 mV / s. These results showed a significant increase (forty times greater) in the current density peaks corresponding to the oxidation of ethanol by the CR5% sample with respect to the NAFION® sample. The increase in the peak current density in the CV measurement may be due to the adsorption of ethoxy groups on the surface of the CR5% and the Ni / CeO2 on the working electrode, around 0.35 V, reaching a peak value of 9.52 mA / cm2at 0.50 V on the forward scan voltage. In the reverse scan voltage, a second ethanol oxidation peak at a current density of 12.22 mA / cm2was observed that may be due to the adsorption of the ethoxy groups of fresh ethanol on the surface of CR5% and Ni / CeCh.

[0062] When comparing the values of the peak current densities between CR5%+Ni / CeO2 and NAFION®+Ni / CeO2, there were significant differences between the systems (FIG. 8). Without being bound by any theory, this difference in peak current density may indicate the CR5%+Ni / CeO2 membrane forms a higher amount of oxygen vacancies at the surface, resulting in a higher amount of reduced metal cations (Ti+, Ce+), possibly facilitating anchoring of ethoxy groups on the electrode surface. In comparison, the NAFION®+Ni / CeO2 membrane only included C-F and S=O groups, thus the availability of reduced metal cations was limited for the anchoring of ethoxy groups on the electrode surface, resulting in a small current density (FIG. 8).

[0063] FIGS. 9A and 9B are CVs of CR5% with Ni / CeCh (10 wt.% Ni) (FIG. 9A) and NAFION® with Ni / CeCh 10 wt.% Ni (FIG. 9B) at different scan rates from 10 mV / s to 100 mV / s in a solution of 1 M KOH and 1 M ethanol. A progressive increase in the peak current density was observed as the scan rate increased, which indicated a direct proportionality relationship between the peak currents and the square root of the corresponding scan rate. This direct proportionality relationship is shown in FIGS. 10A and 10B. FIGS. 10A and 10B are graphs of current vs. square root of scan rate for CR5% with Ni / CeO2 (10 wt.% Ni) (FIG. 10A) and NAFION® with Ni / CeO210 wt.% Ni (FIG. 10B). In FIGS. 10A and 10B, straight lines with a positive slope indicate direct proportionality relationship for the different peak currents both for the CR5% + Ni / CeO2and the Nafion + Ni / CeO2, respectively.

[0064] FIGS. 11 A and 1 IB are CVs of CR5% with Ni / CeO2(10 wt.% Ni) (FIG. 11 A) and NAFION® with Ni / CeO210 wt.% Ni (FIG. 1 IB) at 20, 40, and 60 cycles at a scan rate of 50 mV / s in a solution of 1 M KOH and 1 M ethanol. The progressive decrease of the peak current density was observed over 20-60 cycles.

[0065] FIG. 12 is a graph of energy dispersive X-ray spectroscopy (EDS) spectra of carrageenan (CR), carrageenan with a concentration of 0.1 wt.% of TiO2nanoparticles (NPs) (CR0.1%), carrageenan with a concentration of 0.5 wt.% of TiO2NPs (CR0.5%), carrageenan with a concentration of 1 wt.% of TiO2NPs (CR1%), carrageenan with a concentration of 5 wt.% of TiO2NPs (CR5%). EDS was used to study the chemical composition and the relative abundance of the elements in the nanocomposite samples. For this reason, EDS measurements were conducted as shown in FIG. 12, for each of the different membranes (CR, CR0.1%, CR0.5%, CR1% and CR5%). In the CR0.1% membrane, main peaks corresponding to the S, O, and C elements were observed, which may correspond to the main components of the polysaccharide structure of K-carrageenan and k-carrageenan, which are present in all membranes. The peaks corresponding to the K, Cl, Na, Ca ions may belong to inorganic salts, which are found in commercial carrageenan. These peaks of the inorganic salts were also found in the XRD measurements (see FIG. 2). When the CR membrane was doped with different concentrations of TiO2NPs, the appearance of the Ti element in the CR0.1% membrane was observed around 0.46 keV, 4.52 keV, and 4.94 keV. For these last two energy values, a progressive increase in intensity was observed as the TiO2NPs concentration increased, until it reaches a higher value in the CR5% membrane.

[0066] FIGS. 13 A and 13B are CVs comparing CR5% with Ni / CeCh to CR5% with CeCh, Y-AI2O3, and Ni / y-AhOs (FIG. 13 A) and comparing NAFION® with Ni / CeCh to NAFION® with CeCh, Y-AI2O3, and Ni / y-AhCh (FIG. 13B). In FIG. 13A, no electro-oxidation of ethanol is observed in the cells using electrodes made of CR5% with CeCh, Y-AI2O3, or Ni / y- AI2O3. Electro-oxidation is only observed in FIG. 13A in the cell using an electrode made of CR5% with Ni / CeCh. Similarly, in FIG. 13B, no electro-oxidation of ethanol is observed in the cells using electrodes made of NAFION® with CeO2, y-AEOs, or Ni / y-AhOs. Electrooxidation is only observed in FIG. 13B in the cell using an electrode made of NAFION® with Ni / CeO2.EQUIVALENTS

[0067] While certain embodiments have been illustrated and described, a person with ordinary skill in the art, after reading the foregoing specification, can effect changes, substitutions of equivalents and other types of alterations to the compounds of the present technology or salts, compositions, derivatives, and mixtures as set forth herein. Each aspect and embodiment described above can also have included or incorporated therewith such variations or aspects as disclosed in regard to any or all of the other aspects and embodiments.

[0068] The present technology is also not to be limited in terms of the particular aspects described herein, which are intended as single illustrations of individual aspects of the present technology. Many modifications and variations of this present technology can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods within the scope of the present technology, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. It is to be understood that this present technology is not limited to particular methods, reagents, compounds, compositions, labeled compounds or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting. Thus, it is intended that the specification be considered as exemplary only with the breadth, scope and spirit of the present technology indicated only by the appended claims, definitions therein and any equivalents thereof.

[0069] The embodiments, illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising,” “including,” “containing,” etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed technology. Additionally, the phrase “consisting essentially of’ will be understood to include those elements specifically recited and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase “consisting of’ excludes any element not specified.

[0070] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

[0071] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0072] All publications, patent applications, issued patents, and other documents (for examplejournals, articles and / or textbooks) referred to in this specification are herein incorporated by reference as if each individual publication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by referencein its entirety. Definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure.

[0073] The present technology may include, but is not limited to, the features and combinations of features recited in the following lettered paragraphs, it being understood that the following paragraphs should not be interpreted as limiting the scope of the claims as appended hereto or mandating that all such features must necessarily be included in such claims:A. A fuel cell electrode comprising: about 1 wt.% to about 10 wt.% carrageenan; about 0.5 wt.% to about 50 wt.% metal oxide having a dimension of about 0.1 nm to about 100 nm; and about 1 wt.% to about 20 wt.% of a catalyst comprising CeCh and a metal catalyst.B. The fuel cell electrode of Paragraph A, wherein the carrageenan comprises a mixture of K- carrageenan and X-carrageenan.C. The fuel cell electrode of Paragraph A, wherein the carrageenan comprises K-carrageenan.D. The fuel cell electrode of any one of Paragraphs A-C, wherein the fuel cell comprises about 1 wt.% to about 5 wt.% carrageenan.E. The fuel cell electrode of any one of Paragraphs A-D, wherein the metal oxide comprisesTiCh, CeCh, ZrCh, or a mixture of two or more thereof.F. The fuel cell electrode of Paragraph E, wherein the metal oxide comprises nanoparticles.G. The fuel cell electrode of any one of Paragraphs A-D, wherein the metal oxide comprisesTiCh nanoparticles, TiCh nanorods, TiCh nanotubes, TiCh nanofibers, or a mixture of two or more thereof.H. The fuel cell electrode of any one of Paragraphs A-D, wherein the metal oxide comprisesTiCh nanoparticles.I. The fuel cell electrode of any one of Paragraphs A-H, wherein the fuel cell electrode comprises about 1 wt.% to about 10 wt.% metal oxide.J. The fuel cell electrode of any one of Paragraphs A-I, wherein the fuel cell electrode comprises about 5 wt.% metal oxide.K. The fuel cell electrode of any one of Paragraphs A- J, wherein the metal catalyst comprises nickel, copper, cobalt, iron, ruthenium, rhodium, palladium, platinum, silver, or a mixture of two or more thereof.L. The fuel cell electrode of any one of Paragraphs A-K, wherein the metal catalyst is nickel disposed on a surface of CeCh particles in a ratio of Ni to CeCh of about 1 :9.M. The fuel cell electrode of any one of Paragraphs A-L, wherein the fuel cell electrode comprises about 5 wt.% to about 15 wt.% metal catalyst.N. The fuel cell electrode of any one of Paragraphs A-M, wherein the fuel cell electrode comprises about 10 wt.% metal catalyst.O. The fuel cell electrode of any one of Paragraphs A-N, further comprising about 1 wt.% to about 10 wt.% sulfonated tetrafluoroethylene based fluoropolymer-copolymer.P. The fuel cell electrode of any one of Paragraphs A-O, wherein the fuel cell electrode has an ionic conductivity at about 20 °C of 10'4S / cm or greater.Q. The fuel cell electrode of any one of Paragraphs A-P, wherein the fuel cell electrode produces a current density for the electrooxidation of ethanol in an electrolyte of 1 M ethanol and 1 M KOH of 9 mA / cm2or greater.R. A method of forming the fuel cell electrode of any one of Paragraphs A-Q, the method comprising: forming an aqueous solution of carrageenan with the metal oxide and the catalyst dispersed therein; andforming the fuel cell electrode by casting and drying the aqueous solution.S. A fuel cell comprising: the fuel cell electrode of any one of Paragraphs A-R; a counter electrode; and a polymer electrolyte membrane disposed between the fuel cell electrode and the counter electrode.T. The fuel cell of Paragraph S, wherein the fuel cell is a direct ethanol fuel cell.

[0074] Other embodiments are set forth in the following claims, along with the full scope of equivalents to which such claims are entitled.

Claims

1. WHAT IS CLAIMED IS:

1. A fuel cell electrode comprising: about 1 wt.% to about 10 wt.% carrageenan; about 0.5 wt.% to about 50 wt.% metal oxide having a dimension of about 0.1 nm to about 100 nm; and about 1 wt.% to about 20 wt.% of a catalyst comprising CeCh and a metal catalyst.

2. The fuel cell electrode of Claim 1, wherein the carrageenan comprises a mixture of K- carrageenan and X-carrageenan.

3. The fuel cell electrode of Claim 1, wherein the carrageenan comprises K-carrageenan.

4. The fuel cell electrode of Claim 1, wherein the fuel cell comprises about 1 wt.% to about 5 wt.% carrageenan.

5. The fuel cell electrode of Claim 1, wherein the metal oxide comprises TiCh, CeCh, ZrCh, or a mixture of two or more thereof.

6. The fuel cell electrode of Claim 5, wherein the metal oxide comprises nanoparticles.

7. The fuel cell electrode of Claim 1, wherein the metal oxide comprises TiCh nanoparticles,TiCh nanorods, TiCh nanotubes, TiCh nanofibers, or a mixture of two or more thereof.

8. The fuel cell electrode of Claim 1, wherein the metal oxide comprises TiCh nanoparticles.

9. The fuel cell electrode of Claim 1, wherein the fuel cell electrode comprises about 1 wt.% to about 10 wt.% metal oxide.

10. The fuel cell electrode of Claim 1, wherein the fuel cell electrode comprises about 5 wt.% metal oxide.

11. The fuel cell electrode of Claim 1, wherein the metal catalyst comprises nickel, copper, cobalt, iron, ruthenium, rhodium, palladium, platinum, silver, or a mixture of two or more thereof.

12. The fuel cell electrode of Claim 1, wherein the metal catalyst is nickel disposed on a surface of CeCh particles in a ratio of Ni to CeCh of about 1 :9.

13. The fuel cell electrode of Claim 1, wherein the fuel cell electrode comprises about 5 wt.% to about 15 wt.% metal catalyst.

14. The fuel cell electrode of Claim 1, wherein the fuel cell electrode comprises about 10 wt.% metal catalyst.

15. The fuel cell electrode of Claim 1, further comprising about 1 wt.% to about 10 wt.% sulfonated tetrafluoroethylene based fluoropolymer-copolymer.

16. The fuel cell electrode of Claim 1, wherein the fuel cell electrode has an ionic conductivity at about 20 °C of 10'4S / cm or greater.

17. The fuel cell electrode of Claim 1, wherein the fuel cell electrode produces a current density for the electrooxidation of ethanol in an electrolyte of 1 M ethanol and 1 M KOH of 9 mA / cm2or greater.

18. A method of forming the fuel cell electrode of Claim 1, the method comprising: forming an aqueous solution of carrageenan with the metal oxide and the catalyst dispersed therein; and forming the fuel cell electrode by casting and drying the aqueous solution.

19. A fuel cell comprising: the fuel cell electrode of Claim 1; a counter electrode; and a polymer electrolyte membrane disposed between the fuel cell electrode and the counter electrode.

20. The fuel cell of Claim 19, wherein the fuel cell is a direct ethanol fuel cell.

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