System for desalination and conversion of saltwater or concentrated water to freshwater and water treatment and energy storage through desalination resources, and system for producing chemicals through discharge process

Abstract

The present invention relates to a saltwater-to-freshwater conversion and charging system for water treatment and energy storage through desalination resources, wherein saltwater is subjected to desalination and wastewater purification, a NaxC cathode is charged using electrons generated from an anode, and the charged NaxC cathode is discharged to produce additional chemicals. Saltwater is desalinated to produce freshwater, desalinated chloride ions are purified at a photoanode through an oxidation reaction, and at the same time electrons generated through the oxidation reaction move to a NaxC cathode and electrochemically charge the NaxC cathode with the desalinated sodium, and additional chemicals such as such as hydrogen, hydrogen peroxide, and formic acid can be produced through a process that involves discharging the charged NaxC cathode.

Description

A system that desalinates and desalinizes salt water or concentrated water, treats water using desalinated resources, and stores energy, and produces chemicals through a discharge process.

[0001] This study (results) was conducted as part of the National Water Industry Cluster's mini-cluster project lab project.

[0002] This work is financially supported by Korea Water Cluster (KWC) as 「Korea Water Cluster ProjectLab」

[0003] The present invention relates to a salt water or concentrated water desalination charging system for water treatment and energy storage using desalinated resources, wherein wastewater is purified using desalinated chloride ions, and desalinated sodium ions are converted to Na using electrons generated at an oxidation electrode. x Charge the C reduction electrode, and charge the Na x The present invention relates to a system for water treatment and energy storage using solar energy and electric energy, characterized by discharging a C reduction electrode to produce additional chemicals such as hydrogen, hydrogen peroxide, or formic acid.

[0004] Producing carbon-neutral chemicals and securing clean water have been considered the most critical challenges facing humanity over the past 50 years. Among the technological solutions proposed to address these challenges, photoelectrocatalytic (PEC) systems, which operate on infinite, carbon-free solar energy, have proven to be environmentally benign and technologically feasible. For example, a PEC device with 10% efficiency produces an average daily power of approximately 250 Wm . -2 Under standard terrestrial 1-sun conditions, clean water is decomposed into about 0.7 gs -1Hydrogen molecules can be produced in . Considering the maritime transport of H2 and liquid carriers (e.g., ammonia), PEC systems must be operated near coastal areas with abundant saltwater for low-cost production. However, obtaining clean water from saltwater is energy-intensive and generates a significant carbon footprint, thus weakening the techno-economic advantages of PEC systems.

[0005] Recently, PEC desalination systems have been proposed for hybrid water reuse and chemical production by solar energy. Unlike conventional PEC reactions, PEC desalination mimics electrodialysis in terms of system configuration. The key feature of the PEC desalination process is that it simultaneously induces many valuable reactions in a single device. In particular, desalinated Cl - is a reactive chlorine species (RCS, HOCl / OCl) - ) is oxidized to Na, which effectively mediates the oxidation of aqueous pollutants in the photoelectrode zone. Desalinated Na + are simultaneously accumulated in the cathode zone and increase the conductivity of the solution in the reduction reactor, thereby assisting the H2 production reaction (HER) and the CO2 reduction reaction (CO2RR). The proof of concept was further demonstrated using a scalable multi-stack PEC desalination device for chloride oxidation reaction (ClOR) and metal composite cathodes for HER and CO2RR. While the substrate was decomposed in the photocatalytic cathode zone, HER or CO2RR occurred at a faradaic efficiency (FE) of over 90%. In brine (salinity 5-36 g L -1 ) has a low specific energy consumption (SEC: 1.1 kWh m -3 ) was carried out. It is estimated that the H2 energy produced as is contributes to additional energy savings of up to 25%-30%.

[0006] The present invention, unlike the prior art, accumulates Na when charging a Na metal electrode. +We note the potential use of this approach. This approach could address the inherent challenges faced by PEC systems, which are limited by the intermittent nature of sunlight, which varies daily and is unavailable at night. The Na metal electrode has a theoretical specific energy (1,165 mAh g -1 ) and high cell voltage (- 2.71 V). With this in mind, a visible light-active photoanode (W-doped BiVO4 deposited with CoOOH) using selective ClOR and brine (NaCl 10 g L -1 ) using aqueous Na metal reduction electrode (Na on carbon felt, Na x We designed a PEC desalination cell containing C). The photocatalytic electrode is particularly suitable for the desalination of less reactive species (e.g., ClO3) under simulated sunlight. - ) were tailored to partially oxidize the desalinated chloride into RCSs while minimizing hyper-oxidation. The RCSs generated in this situation are mixed aquatic contaminants (As 3+ and NH3) effectively mediated the oxidation of Na x C is simultaneously desalinated Na + was photocharged. After the light irradiation was finished, the charged Na x C was used to produce H2O2 via O2 reduction reaction (ORR) (E°= 0.695 V), H2O2 via HER (E°= 0 V), and formic acid via CO2RR (E°= -0.2 V) using designed carbon nanotubes (CNTs), NiMoS, and Bi, respectively. This is the first attempt to demonstrate a solar desalination charger.

[0007] The present invention desalinates salt water and purifies waste water, and uses electrons generated at an oxidation electrode to produce Na x Charge the C reduction electrode and charge the Na xThe present invention relates to a salt water desalination charging system for water treatment and energy storage using a desalination resource that produces additional chemicals by discharging a C reduction electrode, and a system that produces chemicals through a discharge process.

[0008] In one aspect, the present invention comprises a desalination tank having a cation exchange membrane on one side and an anion exchange membrane on the other side, which receives salt water, a reduction reaction tank including a first electrolyte that receives cations from the cation exchange membrane, an oxidation reaction tank including a second electrolyte that receives anions from the anion exchange membrane, and Na located in the reduction reaction tank. x A system for desalination and desalination from salt water, and for water treatment and energy storage using desalinated resources, is claimed, comprising a reduction electrode including C, an oxidation electrode located in the oxidation reaction tank, and a voltage applying means for applying voltage to the reduction electrode and the oxidation electrode. The system of the present invention simultaneously causes a three-way reaction of desalination of salt water, oxidation of As(III) and / or ammonia, and charging of Na ions. Through this three-way reaction, desalination and desalination by desalination of salt water, water treatment using desalinated resources by oxidation of As(III) and / or ammonia, and energy storage by charging of Na ions are possible.

[0009] Preferably, the anode may be a system for desalination and desalination from salt water, and water treatment and energy storage using desalinated resources, comprising tungsten (W)-doped BiVO4. Doping with tungsten (W) enhances charge separation capability and electrical conductivity by suppressing charge recombination without affecting the crystallinity of pure BiVO4. In other words, W-doping improves the electrical conductivity characteristics of the photooxidation electrode of pure BiVO4 and facilitates charge transfer.

[0010] Preferably, the oxidation electrode comprising the tungsten (W)-doped BiVO4 may be a system for desalination and desalination from salt water, and water treatment and energy storage using desalinated resources, further comprising Co(OH)2. The deposition of Co has little effect on the thickness of the electrode, so it does not interfere with light absorption and does not affect the inherent electronic structure of BiVO, while having a larger ICPE (current to incident photon efficiency) value, which greatly helps in charge separation. The Co deposited on the electrode mainly becomes Co(OH)2, which is gradually oxidized to CoOOH. This CoOOH is Cl - FE for RCS production by enabling the catalyst for selective oxidation of RCSs such as HClO ClOR This allows the value to be improved by about 4 to 5 times. That is, by increasing the IPCE value through Co deposition, the charge separation ability is improved and the production capacity of RCSs of the photo-oxidation electrode is increased.

[0011] In another aspect, the present invention comprises an oxidation-reduction reaction tank containing an electrolyte, and Na charged by the system of any one of claims 1 to 3 located in the oxidation-reduction reaction tank. x C oxidation electrode, electrocatalytic reduction electrode located in the oxidation-reduction reaction tank and the Na x A system for producing a chemical substance through a discharge process is claimed, comprising a C oxidation electrode and a means for connecting the electrocatalytic electrode. Na x The C oxidation electrode can oxidize by releasing sodium ions into the oxidation-reduction reaction tank, while at the same time reducing a specific substance at the reduction electrode to produce a value-added chemical substance.

[0012] Preferably, the electrocatalytic reduction electrode may be a system that produces a chemical substance through a discharge process, characterized in that it includes CNT and reduces oxygen molecules (O2) during the discharge process to produce hydrogen peroxide (H2O2). In this case, the electrocatalytic reduction electrode may be a system that produces a chemical substance through a discharge process, characterized in that the hydrogen peroxide production reaction (O2 + 2H + + 2e - → H2O2) occurs.

[0013] Preferably, the electrocatalytic reduction electrode may be a system that produces a chemical substance through a discharge process, characterized in that it includes NiMoS and reduces water molecules (H2O) to produce hydrogen molecules (H2) during the discharge process. In this case, the electrocatalytic reduction electrode may be a system that produces a chemical substance through a discharge process, characterized in that the HER reaction (2H + + 2e - → H2) occurs.

[0014] Preferably, the electrocatalytic reduction electrode may be a system that produces a chemical substance through a discharge process, characterized in that it includes Bi and reduces carbon dioxide molecules (CO2) during the discharge process to produce formic acid (HCOOH). In this case, the electrocatalytic reduction electrode may be a CO2RR reaction (CO2 + 2H + + 2e - → HCOOH) occurs.

[0015] According to the present invention, fresh water is produced by desalinating salt water, and the desalinated chloride ions are purified through an oxidation reaction at a photo-oxidation electrode, and the electrons generated through the oxidation reaction are Na x C moves to the reduction electrode and desalinated sodium is Na x C is electrochemically charged to the reduction electrode.

[0016] In addition, the charged Na x Through the process of discharging the C reduction electrode, additional chemicals such as hydrogen, hydrogen peroxide, and formic acid can be produced.

[0017] Figure 1(a) shows the XRD patterns of the FTO substrate, BVO, WBVO, and Co-WBVO.

[0018] Figure 1(b) shows the XPS spectra of the V 2p and O 1s bands (inset: W 4f band).

[0019] Figure 1(c) and (d) show the XPS spectra of the 2p3 / 2 band of Co for the as-synthesized Co-WBVO and the pre-anodized Co-WBVO, respectively. The percentage numbers in Figure 1(c) and (d) are the deconvoluted Co peaks. 3+ It shows the area fraction of the peak and the optical and electrochemical properties of BVO, WBVO, and Co-WBVO.

[0020] Figure 1(eg) shows the optical and electrochemical properties of BVO, WBVO, and Co-WBVO.

[0021] Figure 1(e) shows the TRPL spectrum, and the inset shows the 2D emission lifetime image and PL spectrum. The white bar represents 20 μm, and the numbers indicate the average emission decay lifetime (τ).

[0022] Figure 1(f) shows the EIS spectrum of 0.171 M NaCl, and the inset shows the estimated charge transfer resistance (R) by fitting the spectrum to the Randle circuit model. ct ) shows the value.

[0023] Figure 1(g) shows the Mott-Schottky plot in 0.171 M NaCl, and the numbers in parentheses are the donor density (N D , x 10 22 cm -3) It represents.

[0024] Figure 2(a) shows linear sweep voltammograms (LSV) to indicate the PEC activity of pure BVO and modified BVO samples in 0.171 M NaCl, with the inset showing E = 1.36 V.RHE Shows the IPCE profile in .

[0025] For Fig. 2(bd), the bulk PEC reaction E = 0.73 V SCE (E = 1.36 V RHE ) was performed in a two-compartment cell. The solution pH changed over time and the SCE scale was used.

[0026] Figure 2(b) is a graph showing the production of RCSs, and the inset shows the faradaic efficiency (FE) for RCS production through chloride oxidation reaction (FEClOR).

[0027] Figure 2(c) shows the oxidation of As(III) (1 mM) to As(V) and the generation of RCS using Co-WBVO.

[0028] Figure 2(d) shows the oxidation of NH3 (1 mM) and nitrate (NO3 - ) shows simultaneous production.

[0029] Figure 3(a-b) shows the PEC charging, and Figure 3(c-d) shows the discharging reaction of the electrocatalyst. In the photocharging step, the photocatalyst was charged with Na in a 0.171 M NaCl solution containing As(III) and NH3. x C electrode (see Fig. 6(a) for experimental setup). In the discharge stage, the charged Na separated from the photo-oxidation electrode x The C electrode was coupled to three different electrocatalysts (CNT, NiMoS, Bi) for O2 reduction in 0.1 M K2SO4 purged with O2 at pH 6.5, H2 production in 0.1 M KOH purged with N2 at pH 13, and CO2 reduction in 0.1 M KHCO3 purged with CO2 at pH 6.8, respectively (see Fig. 6(c) for experimental setup).

[0030] Figure 3(a) shows the linear sweep voltammogram using the photoelectrode and the cell voltage (E) of the photoelectrode and NaxC pair. cell ) shows simultaneous changes.

[0031] Figure 3(b) shows the J = 1 mA cm during the photocharging step. -2 Simultaneous oxidation of As(III)(1 mM) and NH3(1 mM) is shown.

[0032] Figure 3(c) shows the linear sweep voltammogram of the electrocatalyst and the E of the electrocatalyst and charged NaxC pair. cell Shows simultaneous changes in values.

[0033] Figure 3(d) shows the simultaneous production of HCOOH through O2 reduction using CNT, water reduction using NiMoS, and CO2 reduction using Bi during the discharge stage, and the FE values ​​at that time. The numbers in parentheses are the applied J values ​​(unit: mA cm -2 )am.

[0034] Figure 4 shows the solar energy charging process through desalination of brine (0.171 M NaCl) and oxidation of a mixture of As(III) and NH3, using a Co-WBVO photoelectrode with an SCE electrode and Na x The C electrode was immersed in a 0.171 M NaCl solution (see Fig. 6(b) for the experimental setup).

[0035] Figure 4(a) is 1 mAcm -2 J of ph E of Co-WBVO in ph With Co-WBVO and Na x C pair of E cell It represents a change in .

[0036] Figure 4(b) shows Na in brine + and Cl - Changes in and reduction of Na in the reaction vessel + And Cl in the oxidation reactor - Represents positive changes. The inset represents ITE.

[0037] Figure 4(c) shows the changes in As(V) and NH3 concentrations.

[0038] Figure 5 shows the E of applied 0 V cell PEC Na charged in xElectrocatalytic production of H2O2 using CNTs bonded to the C electrode, H2 using NiMoS, and HCOOH using Bi is shown (see Fig. 6(c)).

[0039] Figure 5(a) shows the change in the discharge J value of the electrocatalyst.

[0040] Figure 5(b) shows the change in the potential (Ec) of the electrocatalyst.

[0041] Figure 5(c) shows the production of H2O2, H2, and HCOOH.

[0042] Figure 5(d) shows FEs for chemical production.

[0043] Figure 5(e) shows E at 0 V cell Na charged through LED bulb in x It shows the discharge current density when the electrocatalyst of H2O2 is generated using CNTs bonded to the C electrode.

[0044] Figure 5(f) shows Na charged through an LED bulb. x The electrocatalyst using CNT combined with C electrode shows the H2O2 production and FE values ​​over time when H2O2 is produced.

[0045] Figure 6(a) shows the solar energy charging related to water treatment. Photoelectrode (pure BVO or modified BVO) and Na metal array (Na) in brine with As(III) and NH3 x C) The electrodes were directly bonded. By light, the photoelectrode is Cl - It oxidizes to reactive chlorine species (RCS) that mediate the oxidation of As(III) and NH3. Simultaneously, Na+ ions are converted to Na x Inserted into the C electrode.

[0046] Figure 6(b) shows water treatment and charging related to desalination using solar energy. The two electrodes are separated by anion exchange membrane and cation exchange membrane (AEM and CEM, respectively), and the photoelectrode is placed in salt-free water containing As(III) and NH3. The middle compartment between the two membranes (desalination cell) is filled with salt water. Desalination proceeds by light, and desalinated Cl - Wow Na + undergoes the same reaction as that of Fig. 6(a).

[0047] Figure 6(c) shows the discharge process for producing additional chemicals. Charged Na x The C electrode is coupled to three different electrodes (CNT, NiMoS, and porous Bi) to produce H2O2 through O2 reduction, H2 through H2O reduction, and HCOOH through CO2 reduction, respectively.

[0048] Figure 7 indicates the reference numerals of Figure 6(b).

[0049] Figure 8 indicates the reference numerals of Figure 6(c).

[0050] The reference symbols shown in FIGS. 7 and 8 have the following meanings.

[0051] Brine desalination recharge system for water treatment and energy storage using 100 desalination resources

[0052] 101 Light

[0053] 102 Desalinated water

[0054] 110 Desalination tank

[0055] 111 Anion permeable membrane (AEM)

[0056] 112 Cation-permeable membrane (CEM)

[0057] Desalinated chloride ions passed through 113 AEM(111)

[0058] Desalted sodium ions passing through 114 CEM(112)

[0059] 120 photo-oxidation electrode

[0060] 121 Holes created by light

[0061] 122 Electrons generated at the photo-oxidation electrode

[0062] 130 Na x C reduction electrode

[0063] 131 Sodium array on carbon felt

[0064] 132 Voltage application means

[0065] 140 Oxidizing electrode bath

[0066] 141 RCS

[0067] 142 Purification process using redox reaction

[0068] 150 reduction electrode tank

[0069] 151 Insertion of sodium ions into the reduction electrode

[0070] A system that produces chemicals through a 200-step discharge process

[0071] 210 charged Na x C oxidation electrode

[0072] Na through 211 discharge process x Sodium ion release at the C oxidation electrode

[0073] 220 Electrocatalytic reduction electrode

[0074] 221 CNT electrode reducing oxygen molecules

[0075] 222 NiMoS electrode reducing water molecules

[0076] 223 Porous Bi electrode for reducing carbon dioxide molecules

[0077] 231 Production of hydrogen peroxide

[0078] 232 Production of hydrogen molecules

[0079] 233 Production of formic acid

[0080] 240 Na x Means for connecting the C oxidation electrode and the electrocatalytic electrode

[0081]

[0082] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention is susceptible to various modifications and variations, and thus specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Throughout the description of each drawing, similar reference numerals have been used to designate similar components.

[0083] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, steps, operations, components, parts, or combinations thereof.

[0084] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0085]

[0086] Figure 7 illustrates a system for desalination and desalination of brine or concentrated water, water treatment using desalination resources, and energy storage.

[0087] Referring to FIG. 7, the system (100) of the present invention comprises a desalination tank (110) containing brine having a cation exchange membrane (112) on one side and an anion exchange membrane (111) on the other side, a reduction reaction tank (150) containing a first electrolyte that receives cations from the cation exchange membrane, an oxidation reaction tank (140) containing a second electrolyte that receives anions from the anion exchange membrane, and a Na located in the reduction reaction tank. x It is composed of a reduction electrode (120) including C, an oxidation electrode (130) located in the oxidation reaction tank, and a voltage applying means (132) for applying voltage to the reduction electrode and the oxidation electrode. Specifically, fresh water is generated through a desalination process (102), and desalinated Cl passing through an anion exchange membrane - (113) is oxidized to reactive chlorine species (141, RCS) that mediates the oxidation (142) of pollutants such as As(III) and ammonia at the photo-oxidation electrode (120) by holes (121) generated by light (101). The generated RCS can perform water treatment to purify water by oxidizing pollutants in an aqueous solution (142). The electrons (122) generated through the oxidation reaction move to the reduction electrode through a voltage applying means (132). The desalinated Na that passes through the cation exchange membrane + (114) is inserted (151) into the sodium array (131) on the carbon felt. x Energy can be stored by charging the C reduction electrode.

[0088] Figure 8 illustrates a system for producing chemical substances through a discharge process.

[0089] Referring to FIG. 8, the system (200) of the present invention comprises an oxidation-reduction reaction tank (230) containing an electrolyte, and Na charged by the system of any one of claims 1 to 3 located in the oxidation-reduction reaction tank. x C oxidation electrode (210), electrocatalytic reduction electrode (220) located in the oxidation-reduction reaction tank and the Na x It consists of a means (240) for connecting the C oxidation electrode and the electrocatalytic electrode. The Na charged by the systems for desalination and desalination and water treatment and energy storage through desalination resources x C reduction electrode (130) during the discharge process x C is used as an oxidation electrode (210). Na x The C oxidation electrode oxidizes by releasing sodium ions into the oxidation-reduction reaction tank. The electrons generated by the oxidation process are then Na x C moves to the reduction electrode by means (240) of connecting the oxidation electrode and the electrocatalytic electrode and reduces a specific substance at the reduction electrode. For example, in the case of the CNT electrocatalytic electrode, oxygen molecules (221, O2) are reduced to produce hydrogen peroxide (H2O2) (231). In the case of the NiMoS electrocatalytic electrode, water molecules (222, H2O) are reduced to produce hydrogen molecules (H2) (232). In the case of the porous Bi electrocatalytic electrode, carbon dioxide molecules (223, CO2) are reduced to produce formic acid (HCOOH) (233). In this way, Na x Through the discharge process using the C oxidation electrode, various chemical substances can be produced at the reduction electrode.

[0090]

[0091] 1. Synthesis of substances

[0092] Pure BiVO4 (BVO) and W-doped BiVO4 (WBVO) were synthesized by electrodeposition and calcination. Fluorine-doped SnO2 (FTO) substrates (6-9Ω / sq, Pilkington, approximately 50 nm thick FTO layer coated on soda-lime glass) were cleaned with ethanol (99.9%, Ducksan) under ultrasonication and dried with a N2 stream. For Bi deposition, BiNO3·5H2O (75 mL, 10 mL, Junsei) was dissolved in KI aqueous solution (0.4 M, Sigma-Aldrich) adjusted to pH 1.7 with HNO3 (60%, Dajung). Then, p-benzoquinone (0.23 M, Sigma-Aldrich dissolved in 99.9% ethanol) was added to the Bi solution and stirred for 5 min. The prepared FTO substrate (working electrode) with a Pt rod (counter electrode) and a saturated calomel electrode (SCE, reference electrode) was immersed in a Bi solution and maintained at -0.2 V vs. SCE for 15 min using a potentiostat (Ivium). The Bi-deposited electrode was rinsed with deionized water (18 MΩ cm) and dried under ambient conditions. Then, vanadyl acetylacetonate [VO(C5H7O2)2, 0.2 M, 0.26 mL, Sigma-Aldrich] dissolved in dimethyl sulfoxide (Sigma-Aldrich) was dropped onto the Bi-deposited electrode and annealed at 450°C for 2 h. The sample electrode was immersed in a KOH (1 M) solution for 30 min and then rinsed with deionized water to remove residual V2O5. For the synthesis of WBVO, tungsten chloride (WCl6, Sigma-Aldrich) was added to vanadyl acetylacetonate solution at various concentrations (doping levels were 0.55–2.77 mM, corresponding to 0.3–1.5 at%). When necessary, as-synthesized WBVO samples were diluted with aqueous Co(II) solution [Co(NO3)2·6H2O, 0.After immersion in 1 M, Sigma-Aldrich], the Co-WBVO electrode was biased at −0.9 V vs. SCE with a deposition charge of 5–30 mC (denoted as Co-WBVO). Unless otherwise specified, the W doping level was 0.3 at% and the Co electrodeposition charge was 10 mC. Before photoelectrolysis, the Co-WBVO electrode was subjected to six potential sweeps from −0.4 to 1.5 V vs. SCE.

[0093] For the photocharging process, 4-unit (coin-shaped) cells were arranged with Na metal electrodes (Na on carbon felt, Na x C, 4 TO ONE Co., Ulsan, Korea) were bonded to the photoelectrode. Each array had a top cap, NASICON (Na3Si2Zr2PO 12 , diameter 16 mm, ionic conductivity approximately 2.5 x 10 -3 Scm -1 ), 1 M NaCF3SO3 (Sigma-Aldrich) dissolved in tetraethylene glycol dimethyl ether (Sigma-Aldrich), sodium metal on carbon felt, spacer, spring, and bottom cap. For H2 production, NiMoS (a mixture of Ni2S3 and MoS2) was electrochemically fabricated on a porous Ni substrate. For H2O2 production, multi-walled carbon nanotubes (CNTs) were loaded onto commercial carbon paper (315 μm thick, Sigracet 39 BB). For the reduction of CO2 to formic acid, a porous dendritic Bi electrode was galvanically deposited for 5 s (5 Acm -2 ) was fabricated on a Cu substrate.

[0094]

[0095] 2. Photocatalytic and electrocatalytic activity tests

[0096] Simulated sunlight (AM 1.5G, 100 mWcm) in a single-compartment cell containing 0.171 M NaCl (Daejung, 99%) -2Linear sweep voltammograms (LSV) of pure BVO electrode and modified BVO electrode synthesized under ABET Technologies (ABET Technologies) were in the range of mVs -1 were obtained at a scan rate. SCE and Pt foil were used as the reference and counter electrodes, respectively. Electrochemical impedance spectra and Mott-Schottky plots were obtained in the frequency range of 0.01–100 kHz at 0 V vs. SCE and in the frequency range of 1 kHz at 0.73 V vs. SCE, respectively. The incident photon-to-current efficiency (IPCE) was calculated using the following equation:

[0097] IPCE (%) = 1239.8 (V nm) x J ph x 100% / P light x λ (eq. 1)

[0098] Here, J ph , P light , and λ are the photocurrent densities (mAcm), respectively. -2 ), incident light power (100 mWcm -2 ) and wavelength (nm). Galvanostatic conditions (J ph = mAcm -2 ) PEC activity was investigated for ClOR in a two-compartment cell partitioned by a proton exchange membrane (Nafion 117, Chemours) containing 0.171 M NaCl (pH approximately 6.5).

[0099] For the oxidation of the substrate simultaneously charged with Na ions, the synthesized photoelectrode (working electrode) was charged in a single compartment cell using 0.171 M NaCl containing 1 mM NH3 (NH4Cl, Sigma-Aldrich) and / or 1 mM arsenite [As(III), NaAsO2, Sigma-Aldrich] at about pH 6.5. x C electrode (counter electrode) and SCE were combined. Constant J ph (1 mAcm -2), using a potentiostat (Ivium) and a multimeter (Keysight, 34461A), the photopotential (E) of the working electrode (vs. SCE) was measured. ph ) and photoelectrode and Na x Potential difference between C electrodes (E cell ) were recorded simultaneously. As shown in Fig. 6(b) and Fig. 7, for the simultaneous three-way reaction (desalination of brine (102), oxidation of ammonia and / or As(III) (142), and charging of Na ions (132)), the photooxidation electrode cell (120, 140) of 0.171 M NaCl (20 mL) containing 1 mM As(III) and / or NH3, the desalination cell (110) of brine (0.171 M NaCl, 5 mL), and the reduction electrode compartment of 5 mM NaCl (20 mL) were designed to have an anion exchange membrane (113, AEM, AMI-7001S, Membrane International) and a cation exchange membrane (114, CEM, CMI-7000S, Membrane International). The desalination compartment was operated at a flow rate of 10 mLmin using a peristaltic pump (Ismatec, Reglo ICC). -1 circulated at a constant flow rate of 1 mAcm -2 J ph While applying Cl - and Na + The intercompartmental ions were analyzed by quantitatively analyzing the electrolyte and saline solution.

[0100] As shown in Fig. 6(c), after the PEC process is performed, the charged Na x The C electrode is a CNT electrode in 0.1 M K2SO4 purged with O2 (pH 6.5) for hydrogen peroxide (H2O2) production through O2 reduction, a NiMoS electrode in 0.1 M KOH purged with N2 (pH approximately 13) for H2 production through H2O reduction, or a formic acid (H HCOO) electrode in 0.1 M KOH purged with N2 (pH approximately 13) for CO2 reduction. - ) was wired to a Bi electrode in 0.1 M KHCO3 purged with CO2 (pH 6.8) for production. Before electrolysis of the bulk, charged Na in a single compartment cell xLinear sweep voltammograms (vs. SCE) of each electrocatalyst (working electrode) were obtained with C (counter electrode). -1 and -3 mAcm at the working electrode -2 While applying J, the potential of the working electrode (vs. SCE) and E cell The values ​​(difference between the working electrode and the counter electrode) were recorded simultaneously using a potentiostat and a multimeter, respectively. In addition, the CNT and the charged Na x C was coupled galvanically via direct wiring or via an LED bulb (λ = 566 nm, size 3, forward voltage 1.8-2.2 V, maximum current 20 mA, DFRobot Co).

[0101] During the PEC desalination and discharge process, the fractions were intermittently sampled and analyzed. Anions (Cl - , ClO3 - , NO2 - and NO3 - ) and cations (Na + and NH4 + ) were analyzed using an ion chromatograph (Thermo Fisher Scientific, DIONEX ICS-1100) equipped with a conductivity detector, and an IonPac As-11HC (4 X 250 mm) column was used for anions and an IonPac CS-12A (4 X 250 mm) column for cations. RCSs (HClO / ClO -) was quantified using N,N-diethyl-p-phenylene-diamine reagent (Hach method). As(V) and H2O2 were quantified using the molybdenum blue method and the DMP method, respectively. Formic acid was quantified using a high-performance liquid chromatograph (Waters 2695 separation module) equipped with a dual absorbance detector (Waters 2487, 210 nm) and a column (BIO-RAD, Aminex HPX-87H, 300 mm Х 7.8 mm). H2 was quantified using a gas chromatograph (GC, Agilent 7820) equipped with a thermal conductivity detector (TCD) and a Carboxene 1000 column.

[0102] The parasitic efficiency (FE), specific energy consumption (SEC, for 50% desalination) and ion conduction efficiency (ITE) are calculated using the following equations.

[0103] FE (%) = (amount of product Х 2F ) x 100% / (J x A xt) (eq. 2)

[0104] SEC (kWh m -3 ) = E cell x J x A xt / (volume of brine) (eq. 3)

[0105] ITE (%) = (amount of monovalent ions transported) / (J x A xt) (eq. 4)

[0106] Here, F, E cell , J, A, and t are the Faraday constants (96,485 C mol -1 ), operating cell voltage (V), operating current density (mA cm -2 ), electrode area (cm 2 ) and time (s). In Eq. 2, the product refers to a chemical produced from two electron-carrying substances (i.e., HClO, H2O2, H2, and HCOOH). When necessary, "V versus SCE" is V RHE= V versus SCE + 0.241 + 0.059 x pH By the formula V RHE was converted to .

[0107]

[0108] 3. Surface characterization

[0109] The top and cross-sectional morphologies of the synthesized pure BVO and modified BVO samples were examined using a field emission scanning electron microscope (FE-SEM, SU8200, Hitachi). The crystalline structure and bonding state of the components of the samples were investigated by X-ray diffraction (XRD; Empyrean, Malvern Panalytical) using Cu-Ka radiation (40 kV and 30 mA) and X-ray photoelectron spectroscopy (XPS; Nexsa, Thermo Fisher Scientific) using Al-Kaα radiation (hn = 1486.6 eV), respectively. The transmittance of the samples was examined using a UV-visible superposition spectrometer (Shimadzu, UV-2450). Time-resolved photoluminescence (TRPL) studies were performed using a confocal microscope (MicroTime-200, Picoquant, Germany). The lifetime measurements were performed at the Korea Basic Science Institute in Daegu Center. A single-mode pulsed diode laser (375 nm wavelength, operating at a repetition rate of 2 MHz, a pulse width of 30 ps, ​​and an average power of approximately 10 μW) was used as the excited state source. Steady-state PL spectra were obtained by guiding the emitted photons through an optical fiber to an external spectrometer (F-7000, Hitachi).

[0110]

[0111] 4. Photoelectrocatalytic activity of the synthesized electrode

[0112] The synthesized BVO sample exhibited a typical single-system crystal structure (ICDD# 04-010-5713) (Fig. 1a). W-doping did not affect the crystallinity of BVO. Neither the W- nor Co-induced XRD peaks (e.g., WO3 and Co2O3, respectively) were observed in WBVO and Co-WBVO due to the trace amount of doped W and deposited Co. The pure BVO and modified BVO samples showed the same morphology grown through particle-to-particle connection, and the total film thickness was approximately 1.8 mm. Meanwhile, XPS analysis of Co-WBVO clearly revealed the presence of W and Co. The atomic level of W was estimated to be 0.25% with respect to Bi (Fig. 1b). However, W doping did not induce spectral changes in the Bi 4f and V 2p bands. In particular, the oxidation state of the deposited Co was 13.4% with respect to Co. 3+ Co in fraction 2+ (781.6 eV) and Co 3+ (780.5 eV) was mixed (Fig. 1c). After preanodization, Co 3+ The fraction increased to 34% (Fig. 1d). A simultaneous decrease in the intensity of the metal-OH band in the O 1s band was also observed. This change indicates that the deposited Co species was primarily Co(OH)2 and was oxidized to CoOOH through repeated anodic scanning. Co deposition on WBVO did not induce a significant change in film thickness. This further indicates that the thin Co layer did not interfere with light absorption.

[0113] TRPL was used to investigate the charge transfer dynamics of pure BVO and modified BVO films (Fig. 1e). Upon excitation at λ = 375 nm, the PL spectrum exhibited a broad emission band in the λ range of 400–800 nm with a maximum at λ = 650 nm (approximately 1.9 eV) (Fig. 1e inset). This emission band originates from the radiative recombination of photogenerated electron-hole pairs via intermediate trap states within the bandgap. However, the maximum emission intensity was reduced by W-doping and Co-deposition, indicating suppression of charge recombination. The normalized TRPL emission intensity of pure BVO decayed exponentially with an average lifetime (τ) of 27 ns. WBVO exhibited the same decay profile but a relatively smaller τ value (21 ns). Co deposition further reduced the τ value to 15 ns. 2D emission lifetime images showed that the brightness was not uniform across the detected region for BVO and WBVO (Fig. 1e inset). However, Co-WBVO was dark overall due to its fast and uniform charge transfer dynamics. The interfacial charge transfer resistance (R ct ) was also performed to gain insight into the R-values ​​(Fig. 1f). The Nyquist plot was performed for BVO. ct While WBVO and Co-WBVO showed a large semicircle with R of approximately 1.8 kΩ, WBVO and Co-WBVO showed R of approximately 0.3 and 0.18 kΩ, respectively. ct It showed a semicircle with a significantly reduced value R ct The main effect of W(VI)-doping on the reduction of donor density (N D About 3 x 10 22 cm -3 ) due to the increase in BVO(N D About 1.7 x 10 22 cm -3 )(Fig. 1g) improved the electrical conductivity. Co-deposition also improved the R ct It contributed slightly to the decrease, but was insignificant, which is similar to the N of WBVO. D It's just a value.

[0114] Linear sweep voltammograms of pure BVO and modified BVO photooxidation electrodes were obtained in aqueous NaCl solution (0.171 M, pH approximately 6.5) (Fig. 2a). Pure BVO exhibited a ClOR response of approximately 1.45 mA cm -2 J of ph about 0.8 V RHE Onset potential (E on ) was shown (J ph,ClOR , E°(Cl2 / Cl - ) = 1.36 V RHE ) W-doping has a significant effect on the voltammogram, with the lowest E at doping levels of 0.3-0.6 at%. on (about 0.6 V RHE ) and the highest J ph,ClOR (2.4 mA cm -2 ) results. As shown in Fig. 1e, the main role of W dopant is to enhance charge separation, but excessive doping induces a structural change from single-phase scheelite to tetragonal scheelite. This should reduce the PEC activity at W-doping levels above 0.6 at%. In particular, Co-WBVO showed different voltammograms with repeated potential sweeps. In the first sweep, E on (about 1.7 V RHE ) was about 0.9 V higher than that without Co deposition (i.e., BVO and WBVO), and E was E on When the interval is larger, J ph,ClOR increased dramatically. From the second to the fifth sweep, E on The silver gradually moves to a lower potential of 3.55 mAcm -2 J of ph,ClOR 0.4 V RHEreached. This change in the voltammogram is due to the gradual oxidation of the deposited Co(OH)2 to CoOOH during the oxidation potential sweep (see Figures 1c and 1d). As shown in Figure 1g, this Co oxidation shifts the flatband potential of WBVO from 0 to -0.1 V. RHE The band-bending and charge separation were enhanced by moving to . Moreover, the optimal charge for Co deposition was 10 mC. Further deposition at 30 mC degenerated Co-WBVO. The IPCE value of Co-WBVO was larger than those of BVO and WBVO, which was due to J ph It matches the profile (Fig. 2a inset). However, J ph The onset wavelengths of the generation and IPCE were approximately 505 nm for pure BVO and modified BVO photoelectrodes due to their similar band gaps of 2.45 eV. This indicates that the adopted surface modification enhanced the charge transfer efficiency without affecting the intrinsic electronic structure of BVO.

[0115] 1.36 V RHE In ClOR, a positive charge (H + ) was further investigated in a cell with two compartments separated by a membrane (Fig. 2b). With pure BVO, approximately 1.5 mA cm -2 Stable Jph,ClOR flows over 60 minutes, and photogenerated holes (121, h + ) were generated via ClOR (reaction schemes 1 and 2).

[0116] 2Cl - + 2h + → Cl2(1)

[0117] Cl2+ H2O → HClO + Cl - + H + (2)

[0118] RCSs production (FE ClOR ) was about 40% in the initial stage (Fig. 2b inset). W-doping was Jph,ClOR (about 2.4 mAcm -2 ) significantly increased, but FE ClOR (about 48%) slightly increased. This indicates that the main effect of W-doping was to enhance charge separation, with a minor contribution to charge injection (i.e., catalytic reaction). With Co-WBVO, the RCS production was about 90% (J ph,ClOR About 3.55 mAcm -2 ) of FE ClOR The RCS production was improved from 4 to 5 times. In particular, the RCS production leveled off in the later stages of all three photoelectrode PEC reactions. Considering that the diffusion of HClO into the counter electrode compartment was inhibited by the membrane, the observed leveling off phenomenon is likely due to the inhibition of HClO diffusion into the counter electrode compartment by the formation of chlorate (ClO3 - ) because it was oxidized to Cl. Nevertheless, the FE value for chlorate oxidation (about 10%) using Co-WBVO was significantly lower than that of BVO (about 30%) and WBVO (about 20%), which means that the deposited CoOOH was oxidized to Cl. - It shows that it catalyzed the selective oxidation of HClO.

[0119] The produced RCS was active in the oxidation situation of As(III) to As(V) (Scheme 3). E = 1.36 V in NaCl solution. RHE Using the WBVO of As(V), As(V) is 0.45 min -1 The apparent rate constant (k) of app ) was produced (Fig. 2c). Using Co-WBVO, As(V) production was 0.78 min -1 k of app was significantly enhanced. RCS was produced immediately after the complete oxidation of As(III) (about 60 min), which confirmed that RCS was a primary reactive species. The amount of RCS did not increase further for about 120 min, indicating that ClO3 of HClO -This is due to the simultaneous oxidation of As(III). The decomposition of ammonia was also investigated (Fig. 2d). Similar to the case of As(III) oxidation, Co-WBVO exhibited faster decomposition kinetics than WBVO. In both photoelectrodes, ammonia decomposition was accompanied by the gradual production of nitrate. Even after complete decomposition of ammonia, N-chloramine intermediates (e.g., NH) by HClO were produced. 3-x Cl x ) continued to produce nitrates (equations 4 and 5). The slower oxidation of ammonia compared to As(III) is due to the eight-electron transfer reaction, which requires four HClO molecules per mol of ammonia molecule.

[0120] As III (OH)3+ HClO → H2As V O - + Cl - + 2H + (3)

[0121] NH3+ xHClO → NH 3-x Cl x + xH2O (4)

[0122] NCl3+ HClO + 2H2O → NO3 - + 4Cl - + 5H + (5)

[0123]

[0124] 5. PEC charging and electrocatalytic discharge reactions

[0125] To drive the PEC ClOR and charge it with sodium ions, WBVO and Co-WBVO photoelectrodes were arranged in an aqueous NaCl solution containing both As(III) and NH3. x C electrode was coupled. Figure 3a shows the linear sweep voltammogram at the photoelectrode and the photoelectrode and Na x Cell voltage of C array electrode pair (E cell) shows simultaneous changes. As shown in Fig. 2a, the overall voltammogram profile was similar to that of the conventional one using a Pt counter electrode. However, Na x J of C ph was larger than that of Pt. Many Na x Increasing the unit of C electrode is J ph Improve the value. Na x Na of C + Insertion (charging) dynamics of Pt + It appears to be comparable to oxidation and partially affects the behavior of the photoelectrode. As the potential bias increases, E cell Silver Na x It increased linearly due to the PEC charge of C, but with more units of Na x The increase was less pronounced along the C electrode. 1 mAcm -2 J of ph When applied to WBVO and Co-WBVO, approximately 0.7 and 0.5 V SCE (1.06 and 0.86 V respectively RHE ) of the photovoltaic potential (E ph ) was maintained for 8 hours, and E cell were about 4.0 and about 3.7 V, respectively. Co-WBVO and Na x During PEC ClOR with simultaneous charging of the C array, As(III) was continuously oxidized to As(V) for 4 h (Fig. 3b). Immediately after the As(III) oxidation was completed, ammonia decomposition began and was completed in 8 h. Similar behavior was observed in WBVO with delayed kinetics. As shown in Fig. 2b, the same J ph Despite its value, the relatively fast decomposition rate of Co-WBVO is due to its larger FE ClOR It could be because.

[0126] After PEC process, 8mAh(=1 mAcm -2 x 1 cm 2 Charged Na (x 8 h) xThe C electrode was coupled to CNT, NiMoS, and porous Bi electrodes specifically designed for the production of H2O2, H2, and HCOOH (representing formic acid and formate) through the reduction of O2, H2O, and CO2, respectively, under various conditions (Schemes 6-8).

[0127] O2+ 2H + + 2e - → H2O2(6)

[0128] 2H + + 2e - → H2(7)

[0129] CO2+ 2H + + 2e - → HCOOH (8)

[0130] The voltammogram of the synthesized CNT electrode is CNT-Na x Open circuit E at 2.5 V for C pair cell 0.2 V corresponding to RHE E of on (Fig. 3c). Reduction electrode J CNTs is the negative E of the negative CNT CNTs As the potential increased, the value of the negative electrode J using CNT also increased linearly, while E cell Silver Na x It decreased due to the discharge process using C. -1 mAcm -2 A constant J CNTs At 0.035 V RHE and E of about 2.25 V cell was maintained for 3 h. Simultaneously, H2O2 was generated linearly over time with an FE >80% (Fig. 3d). The obtained FE values ​​indicate that the process after PEC charging and post-discharging was successful.

[0131] The voltammograms of NiMoS and Bi electrodes show that the HER and CO2RR are about 0.2 and 0.7 V higher than the H2O2 production reaction, respectively. on It was shown that the value is required. This causes the open circuit E cellThe values ​​decreased to 1.85 and 1.48 V respectively. -1 mAcm -2 At constant J, H2 and HCOOH are produced linearly over 3 h, while at constant potential (E respectively) NiMoS = -0.085 V RHE and E Bi = -0.7 V RHE ) and E cell (1.8 and 1.27 V, respectively) were maintained. The FE for H2 production was approximately 80%. In contrast, the FE for HCOOH production was lower by approximately 60%. In a previous study, the optimal potential of the Bi electrode for CO2RR was approximately -0.85 V. RHE On the other hand, -0.7 V RHE E of Bi In , FE was reduced to about 55%. Therefore, J Bi Ga -3 mA cm -2 When increasing to -0.8 V RHE Stable E of Bi was obtained and the FE for HCOOH production was increased to more than 80%. H2O2 and H2 production were also -3 mAcm with FE more than 80%. -2 was improved in J. However, Na x C electrode is -3 mA cm -2 It discharges quickly from J to E for about 1 hour. cell dropped it

[0132]

[0133] 6. Na x C's PEC desalination-combined charging

[0134] To combine the PEC charging process with the PEC charging, a photoelectrode compartment containing As(III) and NH3, a desalination compartment containing brine, and a Na x A membrane device consisting of a reduction electrode compartment containing C was designed. As can be seen in Fig. 4a, 1 mA cm -2 A constant J ph When using Co-WBVO in E phis about 0.53V per hour SCE It increases rapidly to about 0.6 V over 10 hours. SCE was stabilized. This behavior showed a similar trend to the case when no desalination process was used. E cell It followed the same trend as Eph and reached about 4.1 V in 10 hours. Meanwhile, Na x The E value of C was maintained at approximately -3.3 V. As can be seen in Fig. 4b, during the PEC charging process, the chloride content in the brine decreased linearly over time, while the chloride content in the aqueous solution in the oxidation reactor increased simultaneously. After 10 hours, the total △Cl of the brine and the aqueous solution in the oxidation reactor - is approximately 0.45 mmol, which is equivalent to unidirectional Cl - indicates that Cl was transported from the brine to the aqueous solution in the oxidation reactor. Therefore, Cl - The ITE for was maintained at approximately 100% for 10 hours (Fig. 4b inset). The SEC for 50% desalination was 7.7 kWhm -3 was estimated to be 1.48 times higher than that in a previous study. Meanwhile, oxidation of As(III) (1 mM) to As(V) was completed in 2 h, and ammonia decomposition proceeded for the following 4 h (Fig. 4c). Similar behavior was observed even in the absence of a desalination compartment (Fig. 3b).

[0135] Na in the desalination compartment + Although the amount of (Na) has been continuously decreasing + In the case of about 100% ITE), Na in the aqueous solution in the reduction reactor + It should be noted that the amount of Cl has changed slightly. - Na is different from + The behavior of Na + Na rapidly enough to maintain the amount unchanged for 10 hours xBecause it was inserted into the C electrode. The inserted Na based on the photocharged 10 mAh + The amount of Na was calculated to be approximately 0.37 mmol. The actual injected Na for 10 hours + Considering that the amount of Co-WBVO is about 0.35 mmol, the charge storage efficiency was estimated to be about 95%. The high FE of Co-WBVO ClOR Due to this, all observed behaviors of Co-WBVO were identical to those of WBVO, except for the faster oxidation kinetics of As(III) and ammonia.

[0136] Photocharged Na x The C electrode was directly wired to the CNT electrode in a single-compartment cell containing K2SO4 (pH 6.5) purged with O2, and E at 0 V. cell Silver Na x was applied to the C and CNT electrode pair (Fig. 5). -24 mA cm -2 J of CNTs was flowing in the initial stage and then rapidly decreased after 20 minutes (Fig. 5a), whereas the initial E CNTs (-0.4 V RHE ) is about 0.3 V in the later stages. RHE increased (Fig. 5b). During the discharge period, the production of H2O2 reached a plateau of about 155 μmol in 1 h with about 80% FE (Figs. 5c and 5d). Photocharged Na x When C was combined with NiMoS electrode for H2 production, J NiMoS J at about 90% FE for H2 production CNTs While E collapsed more rapidly NiMoS was gradually decreased. For the Bi electrode, despite the same two-electron transfer process, J Bi (about 5mA cm -2) and the amount of HCOOH were much lower than those of other electrodes. This behavior of Bi is due to the large potential required for CO2RR. Nevertheless, the FE for HCOOH production was about 80%. Finally, Na x C and CNT electrodes have E of 0 V cell was wired through an LED bulb. The LED light generation produced -2 ​​mA cm over 2 hours. -2 Stable discharge of J CNTs was obtained (Fig. 5e). H2O2 was produced linearly over time when Ferk was 80% or higher (Fig. 5f).

[0137]

[0138] 7. Conclusion

[0139] Cl desalinated so far - It can purify water pollutants through redox reaction and electrons generated by light and deionized Na + A desalination-coupled PEC hybrid system capable of charging a sodium metal battery was demonstrated. Significant efforts were made to synthesize a highly efficient BVO-based photoelectrode through W doping and Co deposition. The optimized Co-WBVO oxidized chloride to RCS at an FE of over 90%, minimizing the production of non-reactive chlorine species. The generated but storable RCS effectively oxidized As(III) to As(V) and mixed As(III) and NH4 + NH4 in solution + were sequentially oxidized to nitrate. During the oxidation electrode reaction with chloride, Na + is wired Na x Successfully inserted into the C electrode. Photocharged Na x C was further demonstrated to induce electrocatalytic conversion of O2 to H2O2 using CNT, H2O to H2 using NiMoS, and CO2 to HCOOH using Bi at FE of approximately 80% or more.

[0140] Na + and Cl - This PEC charge-discharge reaction was successfully incorporated into a desalination process using brackish water in a three-compartment cell with ion exchange membranes. 7.7 kWhm -3 While desalination is in progress in the SEC of Na + and Cl - are approximately 100% of ITE, respectively Na x Unidirectional transport was achieved between the C electrode compartment and the photoelectrode compartment. Despite the proof of concept, the designed PEC hybrid system has potential applications in various fields, including desalination, seawater electrolysis, secondary chemical production, and energy storage.

Claims

1. A desalination tank having a cation exchange membrane on one side and an anion exchange membrane on the other side, which receives salt water; A reduction reaction tank including a first electrolyte that receives cations from the cation exchange membrane; An oxidation reaction tank including a second electrolyte that receives anions from the anion exchange membrane; Na located in the above reduction reactor x A reduction electrode containing C; An oxidation electrode located in the above oxidation reaction tank; and Including a voltage applying means for applying voltage to the reduction electrode and the oxidation electrode, A system for desalination and desalination from salt water, and water treatment and energy storage using desalinated resources.

2. In paragraph 1, The above oxidation electrode comprises tungsten (W) doped BiVO4. A system for desalination and desalination from salt water, and water treatment and energy storage using desalinated resources.

3. In paragraph 2, The above oxidation electrode additionally contains Co(OH)2. A system for desalination and desalination from salt water, and water treatment and energy storage using desalinated resources.

4. An oxidation-reduction reactor containing an electrolyte; Na charged by any one of the systems of claims 1 to 3 located in the above oxidation-reduction reactor x C oxidation electrode; An electrocatalytic reduction electrode located in the above oxidation-reduction reaction tank; and Na above x C comprising a means for connecting the oxidation electrode and the electrocatalytic electrode; A system that produces chemicals through a discharge process.

5. In paragraph 4, The above electrocatalytic reduction electrode comprises CNT, It is characterized by reducing oxygen molecules (O2) during the discharge process to produce hydrogen peroxide (H2O2). A system that produces chemicals through a discharge process.

6. In paragraph 4, The above electrocatalytic reduction electrode comprises NiMoS, It is characterized by reducing water molecules (H2O) during the discharge process to produce hydrogen molecules (H2). A system that produces chemicals through a discharge process.

7. In paragraph 4, The above electrocatalytic reduction electrode comprises Bi, It is characterized by reducing carbon dioxide molecules (CO2) during the discharge process to produce formic acid (HCOOH). A system that produces chemicals through a discharge process.

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