Preparation of hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode and flexible sensing application thereof

Abstract

Preparation of hydrogen vacancy-rich biomass-based carbon / nickel-cobalt composite electrode and flexible sensing application thereof, characterized by using biomass as a carbon source, growing NiCo-LDH on the surface thereof in situ through a solvothermal deposition method, further combining with electrochemical activation treatment to cause irreversible deprotonation of cobalt hydroxyl in the layered double hydroxide, accurately introduce hydrogen vacancies, and form Co-O-H with strong adsorption to cations v Active centers, and constructed hydrogen vacancy-rich composite electrode materials with high specific capacitance and cycle stability. Biomass carbon carrier as a conductive and structural support skeleton effectively inhibited the aggregation of LDH nanosheets. Using the synergistic effect of carbon carrier and hydrogen vacancy, the rapid reversible intercalation and deintercalation of multivalent cations and charge compensation were promoted, which significantly improved the ion diffusion kinetics and redox reaction stability. Based on the above structural characteristics, the composite electrode prepared by the application exhibits excellent ion storage performance in various neutral electrolytes, and can further construct flexible sensing and energy storage integrated devices for real-time signal monitoring of human joint movement.

Description

[0001] This invention belongs to the field of new materials, and in particular relates to the preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode and its flexible sensing application. Background Technology

[0002] Supercapacitors, as a novel type of green electrochemical energy storage device, possess advantages such as fast charge / discharge rates, long cycle life, and high power density, demonstrating broad application prospects in portable electronic devices, new energy vehicles, and smart grids. Electrode materials are the core component of supercapacitors, directly determining the device's energy storage performance. Among them, layered double hydroxides (LDHs), especially nickel-cobalt layered double hydroxides (NiCo-LDHs), have become a research hotspot for supercapacitor cathode materials due to their tunable metal valence states, excellent redox activity, and high theoretical specific capacitance.

[0003] However, NiCo-LDH faces three major technical bottlenecks in practical applications: First, it has an inherent electrostatic repulsion to metal cations in neutral electrolytes, resulting in extremely low specific capacitance in neutral systems, which severely restricts its application in green neutral electrolyte systems; second, NiCo-LDH has poor intrinsic conductivity and high charge transfer resistance; third, its nanosheets are prone to aggregation, resulting in low utilization of active sites and poor rate performance and cycle stability.

[0004] To address the aforementioned issues, existing technologies primarily focus on two aspects: First, introducing hydrogen vacancies through defect engineering to alter the electronic structure of the LDH surface, weakening its electrostatic repulsion towards metal cations, and transforming it from a cation-repellent material into a cation-affinity material, thereby improving its energy storage performance in neutral electrolytes. Second, compositing NiCo-LDH with carbon materials, utilizing the high conductivity and porous structure of the carbon support to construct a conductive network, inhibiting nanosheet aggregation, and accelerating charge transfer and ion diffusion. However, existing technologies still have the following shortcomings: (1) A single strategy is difficult to achieve synergistic effect: Although defect engineering alone can improve the affinity of LDH for cations, it cannot solve the problems of poor conductivity and easy aggregation of nanosheets; although carbon composite alone can improve conductivity, it fails to fundamentally solve the problem of LDH's repulsion of cations.

[0005] (2) Limited sources of traditional carbon carriers: Existing technologies mostly use carbon materials such as graphene and carbon nanotubes as composite carriers. However, graphene has high preparation costs and difficult process control, and carbon nanotubes have limited specific surface area. Both rely on fossil resources or precious metal precursors, which does not conform to the concept of green environmental protection and sustainable resource development.

[0006] This invention proposes using biomass as a carbon source to grow NiCo-LDH in situ on its surface via solvothermal deposition. Further electrochemical activation treatment causes irreversible deprotonation of the cobalt hydroxyl groups in the layered double hydroxide, precisely introducing hydrogen vacancies to form Co-OH with strong cation adsorption. v The active center was used to construct a hydrogen-rich vacancy composite electrode material that combines high specific capacitance and cycle stability. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode and its flexible sensing application.

[0008] To achieve the above objectives, the technical solution adopted in this invention includes: using biomass as a carbon source, growing NiCo-LDH in situ on its surface via solvothermal deposition, and further combining this with electrochemical activation treatment to cause irreversible deprotonation of the cobalt hydroxyl groups in the layered double hydroxide, precisely introducing hydrogen vacancies to form Co-OH with strong adsorption for cations. v The active center was used to construct a hydrogen-rich vacancy composite electrode material that combines high specific capacitance and cycle stability.

[0009] The advantages of this invention are:

[0010] (1) The present invention uses biomass as a carbon source, which is eco-friendly and low-cost. Different types of carbon sources are universally applicable to the preparation of biomass-based carbon / nickel-cobalt composite materials.

[0011] (2) In this invention, hydrogen vacancies can expose lattice oxygen atoms as active centers for storing metal cations, thereby weakening the electrostatic repulsion between metal cations and LDH.

[0012] (3) This invention utilizes the synergistic effect of carbon support and hydrogen vacancies to promote rapid and reversible insertion and extraction of multivalent cations and charge compensation, thereby significantly improving ion diffusion kinetics and redox reaction stability.

[0013] (4) The hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite material provided by the present invention has good compatibility with multi-metal salt electrolytes.

[0014] (5) The hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite material provided by the present invention has both high specific capacitance and cycle stability. The device composed of it has both good flexibility and sensitivity, and shows good application prospects in flexible sensing and portable wearable devices. Attached Figure Description

[0015] Figure 1 This is a SEM image of the composite material from Example 1.

[0016] Figure 2This is a schematic diagram of the H vacancy in the composite material of Example 1.

[0017] Figure 3 The infrared spectrum of the composite material in Example 1 is shown.

[0018] Figure 4 The ion storage performance of the composite material in Example 1 before and after ECA treatment in different electrolytes is shown.

[0019] Figure 5 The sensor device based on the composite material in Example 1 shows the signal detection curve of finger joint bending. Detailed Implementation

[0020] The embodiments of the present invention will be described in further detail below: The preparation of a hydrogen-vacancy-rich biomass-based carbon / nickel-cobalt composite electrode and its flexible sensing application are disclosed. The electrode is characterized by: using biomass as the carbon source, in-situ growth of NiCo-LDH on its surface via solvothermal deposition, followed by electrochemical activation treatment to induce irreversible deprotonation of the cobalt hydroxyl groups in the layered double hydroxide, precisely introducing hydrogen vacancies to form Co-OH with strong cation adsorption. v The active center was used to construct a hydrogen-rich vacancy composite electrode material that combines high specific capacitance and cycle stability.

[0021] The present invention will now be further described with reference to embodiments, but it is not limited to any one of these embodiments or similar examples.

[0022] Example 1 Before use, pine wood powder (40-60 mesh) was dried overnight at 105℃. The concentration of p-toluenesulfonic acid solution was 500 g / L, and the mass ratio of p-toluenesulfonic acid to the above biomass was 5:1. Then, it was transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene and reacted at a solvothermal temperature of 120℃ for 1.5 h. After the reaction, the sample was washed sequentially with deionized water and anhydrous ethanol by vacuum filtration, and then dried at 80℃ for 3 h.

[0023] Anhydrous ethanol and deionized water were mixed in a 5:1 ratio as the solvent, and CTAB was selected as the surfactant, with a CTAB to composite carbon support mass ratio of 6:1. Ni and Co were weighed according to a mass ratio of 1:3 and a Ni to composite carbon support mass ratio of 1:4, and added to the anhydrous ethanol / deionized water mixture, which was stirred for 10 min. The mixture was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) and reacted at a solvothermal temperature of 180 °C for 12 h. After the reaction, the sample was washed sequentially with deionized water and anhydrous ethanol using a vacuum filtration method, and then dried at 80 °C for 3 h.

[0024] Cyclic voltammetry was used at a scan rate of 100 mV / s in 1 M KOH solution with an operating potential window of 0–0.3 V. A CHI660E electrochemical workstation was employed, with a biomass-based carbon / nickel-cobalt composite electrode as the working electrode, and a saturated calomel electrode (SCE) and platinum wire as the reference and counter electrodes, respectively, for four cycles.

[0025] The introduction of biomass-based carbon into the composite material prepared in this embodiment constructs a porous structure dominated by mesopores and a continuous conductive network, effectively inhibiting the aggregation of LDH nanosheets. Its interaction with H... v The synergistic effect not only exposed abundant active sites but also weakened the electrostatic repulsion between metal cations and LDH in the neutral electrolyte, with an ion diffusion coefficient of 3.1 × 10⁻⁶. -8 cm 2 A three-electrode system was developed using hydrogen-vacancy-rich biomass-based carbon / nickel-cobalt composite material as the working electrode, a platinum sheet electrode as the counter electrode, and silver / silver chloride as the reference electrode. A 2 M MgSO4 solution was used as the electrolyte, and the specific capacitance was 500 F / g at a current density of 0.5 A / g. A solid-state asymmetric supercapacitor was then fabricated using commercially available activated carbon as the negative electrode, with the solid electrolyte sandwiched between the two electrodes and coated with a polydimethylsiloxane film. This capacitor exhibited high energy and power densities, achieving an energy density of 68 Wh / kg at a high power density of 0.5 kW / kg, and maintaining a cycle stability of 86% after 10,000 cycles. This study overcomes the challenge of LDH's rejection of multivalent cations through a hydrogen vacancy-induced strategy, providing a general pathway for developing high-performance cation supercapacitors utilizing Earth's abundant transition metal resources.

[0026] Example 2 Before use, corn stalks were dried overnight at 105℃. The concentration of p-toluenesulfonic acid solution was 400 g / L, and the mass ratio of p-toluenesulfonic acid to the above biomass was 6:1. The mixture was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) and reacted at a solvothermal temperature of 100℃ for 3 h. After the reaction, the sample was washed sequentially with deionized water and anhydrous ethanol using a vacuum filtration method, and then dried at 60℃ for 4 h.

[0027] Anhydrous ethanol and deionized water were mixed in a 3:1 ratio as the solvent, and CTAB was selected as the surfactant, with a CTAB to composite carbon support mass ratio of 5:1. Ni and Co were weighed at a mass ratio of 1:1 and a Ni to composite carbon support mass ratio of 1:2, and added to the anhydrous ethanol / deionized water mixture, which was stirred for 10 min. The mixture was then transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE) and reacted at a solvothermal temperature of 160 °C for 14 h. After the reaction, the sample was washed sequentially with deionized water and anhydrous ethanol using a vacuum filtration method, and then dried at 80 °C for 3 h.

[0028] Cyclic voltammetry was used at a scan rate of 50 mV / s in 3 M KOH solution with an operating potential window of 0–0.8 V. A CHI660E electrochemical workstation was employed, with the biomass-based char / nickel-cobalt composite sample as the working electrode, and a saturated calomel electrode (SCE) and platinum wire as the reference and counter electrodes, respectively, for 6 cycles.

[0029] In the composite material prepared in this embodiment, the synergistic effect of carbon support and hydrogen vacancies promotes rapid and reversible intercalation / deintercalation and charge compensation of multivalent cations, with an ion diffusion coefficient of 2.9 × 10⁻⁶. -9 cm 2 A three-electrode system was fabricated using a hydrogen-vacancy-rich biomass-based carbon / nickel-cobalt composite material as the working electrode, a platinum sheet electrode as the counter electrode, and silver / silver chloride as the reference electrode. A 2 M LiNO3 solution was used as the electrolyte, and the specific capacitance was 380 F / g at a current density of 0.5 A / g. A solid-state asymmetric supercapacitor was then prepared by sandwiching a solid electrolyte between the two electrodes using commercially available activated carbon as the negative electrode and encapsulating them together with a polydimethylsiloxane film. This capacitor exhibited high energy and power densities, achieving an energy density of 48 Wh / kg at a high power density of 0.8 kW / kg, and maintaining 80% cycle stability after 10,000 cycles. When pressure was applied to the device regularly, the current signal changed rapidly, clearly, regularly, and with strong repeatability, indicating that the device possesses excellent flexibility and sensitivity.

Claims

1. Preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode and its flexible sensing application. Its characteristics are: With biomass as carbon source, NiCo-LDH is grown on the surface of biomass in situ by solvothermal deposition method, and further combined with electrochemical activation treatment to make the cobalt hydroxyl in the layered double hydroxide undergo irreversible deprotonation reaction, accurately introduce hydrogen vacancy, and form Co-O-H with strong adsorption to cations v Active center, and constructs a hydrogen vacancy-rich composite electrode material with high specific capacitance and cycle stability.

2. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: Biomass can be selected from one of sodium lignosulfonate, corn stalks, pine powder, bamboo powder, and fruit peel. The raw materials are dried at 30-120℃ for 6-18 hours with a mesh size of 20-100.

3. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: In the preparation of the carbon support, the concentration of the p-toluenesulfonic acid solution was 200-1000 g / L, the mass ratio of p-toluenesulfonic acid to the above biomass was 1:1-6:1, the solvothermal temperature was 100-220℃, and the reaction time was 0.5-14 h. After filtration and washing, the drying temperature was 30-80℃, and the time was 3-6 h.

4. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: The solvothermal deposition process uses one or more of the following solvents: deionized water, methanol, ethanol, and acetone. The volume ratio of deionized water to organic solvent is 1:1 to 1:

10. The surfactant is one of SDS, CTAB, F127, and DTAB, and the mass ratio of surfactant to composite carbon is 10:1 to 1:

10.

5. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: The mass ratio of Ni to Co is 1:3-10:1, the mass ratio of Ni to composite carbon support is 1:1-1:30, the solvothermal temperature is 80-200℃, and the reaction time is 2-16 h. After filtration and washing, the drying temperature is 30-80℃, and the time is 3-6 h.

6. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: Cyclic voltammetry was used with a scan rate of 50-100 mV / s in 1-6 M alkaline solution, using an operating potential window of 0-1.0 V, for 1-10 cycles.

7. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: The prepared hydrogen-enriched vacancy biomass-based carbon / nickel-cobalt composite material as an electrode has a diffusion coefficient of 2.3 x 10 -9 -3.5 x 10 -8 cm 2 / s.

8. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: With a specific capacitance of 300-600 F / g, this material has good compatibility with multi-metal salt electrolytes such as Na2SO4, LiNO3, MgSO4 and Mg(NO3)2. When used to form solid-state devices, its energy density is 70-25 Wh / kg (power density is 0.5-4 kW / kg), and its cycle stability is 75-90% (10,000 cycles).

9. The preparation of a hydrogen-rich vacancy biomass-based carbon / nickel-cobalt composite electrode according to claim 1 and its flexible sensing application. Its characteristics are: The assembled device can effectively monitor pressing, folding, and human physiological signals, and has good application prospects in fields such as flexible sensing and wearable devices.

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