Preparation And Electrocatalytic Study Of Self - Supporting Electrodes Of CoCr, NiTi, Ni / NiO Layers

Water splitting as a high-efficiency, economical, and eco-friendly technology to generate and store hydrogen fuel, is an important way to solve the energy crisis and environmental governance. For electrolytic water splitting, many factors including the adsorption-desorption of intermediates, electrochemical polarization, Ohmic polarization, concentration polarization and carrier transmission constraints, often cause largeroverpotential resulting in electro-catalytic high consumption of water splitting. For photocatalytic water splitting, the absorption capacityof the photocatalystsor the photoelectrodes for light, the separation efficiency of photo-generated charge, as well as the surface catalytic activity restrict the activity of the catalyst.Thus carry out the work what thephotoelectrocatalyst(PEC) water splitting at room temperature have theoretical and practical significance. Thus, developing catalysts based photoelectron response, which could effectively combine of photochemical and electrochemical advantagesis expected to achieve high-efficient decomposition of water.The main contents of this paper are as follows:1. Co Cr LDH nanosheets were successfully synthesized by a one-step hydrothermal reaction, using urea and NH4 F as the precipitating agent and structure regulator, respectively. Further, a self-supporting Co Cr LDH/carbon fiber paper(CFP) electrodes was built by in-situ growth strategy. In this case, Co and Cr element were the effectiveelectrocatalyticsites and photoactive sites, respectively; moreover, the close contact between Co Cr LDH and conductive substratecould promote charge transmission. The resulting Co Cr LDH/CFP electrodes could significantly reduce the overpotentialof oxygen evolution reaction.2. Ni Ti LDHnanosheets with Ti3+dopingwere also successfully synthesized by a one-step hydrothermal reaction,using urea and NH4 F as the precipitating agent and structure regulator, respectively. And, a self-supporting Ni Ti LDH/carbon fiber paper electrodes were built by in-situ growth strategy. In this case, Ti3 +dopingcould contribute to the narrowed bandgap; while, the surface defects could promote the separation of electrons and holes. The photo-generated electrons could transfer to the collector quickly, and thus reducing the overpotentialof Ni Ti LDH for oxygen evolution reaction during photoelectroreation.3. Thin carbon coated nickel-based nanosheets(Ni@C NSs) were designed andsynthesized by controlling the successive assembly and carbothermal reduction under an inertatmosphere. The nanosheets were assembled by partially reduced Ni nanoparticles and Ni Onanoparticles wrapped in thin graphitic carbon. Dodecyl amine played a vital role in the structuredirectingof the interconnected nanosheets by suppressing the nanoparticles growth and providinga protective effect on the low-valence nickel. The resulting metallic Ni and Ni O were the effective activesites for hydrogen and oxygen evolution, respectively; moreover, the neighboring other nickel speciescould exert a good synergetic effect on the electrocatalytic reaction. The outside thin carbon film wasalso conducive to the electrochemical stability. Furthermore, based on the practical applicationconsiderations, the Ni@C NSs were directly grown on the Ni foam surface. The water electrolyser madeup of Ni@C NSs/Ni foam electrodes presented a 1.57 V cell voltage in an alkaline medium accompaniedwith long-term durability. The highly active transition-metal catalysts with two valences is promising forfull water splitting devices.