Application Of Self-Supported Transition Metal Catalysts In Urea/Hydrazine Assisted Electrolytic Hydrogen Production

With the aggravation of energy crisis and environmental pollution,developing new and clean energy technology has become a research hot-spot.Hydrogen is regarded as a promising energy source carrier because of its high combustion value and combustion products without pollution.Electrocatalytic water decomposition is an efficient and sustainable hydrogen production method.Hydrogen evolution reaction(HER)at cathode and oxygen evolution reaction(OER)at anode are two important half reactions in water electrolysis.The noble metal Pt has been well known as the best catalyst for HER,but its low reserves,high cost and poor stability have seriously limited its large-scale application.Therefore,the development of Pt-like non-noble metal-based catalysts has become a promising way.Constrained by the 4 electrons transfer process,the sluggish OER is the key to limiting efficient water decomposition.Replacing OER with urea or hydrazine oxidation reaction(UOR,HzOR)is an effective way to reduce the voltage in the water decomposition.In this paper,non-noble metal based self-supporting electrode materials with hierarchical structures were designed by reasonable composition design and structure construction,and their structural morphology and electrochemical properties were studied,and the experimental of uninterrupted hydrogen generation driven by solar energy was demonstrated(1)the hierarchical NiCoFeP self-supporting electrode was prepared by potassium ferricyanide etching.This scheme is beneficial to the metal organic frame evenly dispersed on the surface of the primary structure,effectively avoiding active substance agglomeration.The hierarchical structure of the introduced porous metal organic framework effectively increases the active sites of the electrode.The electrode demonstrated excellent full pH HER performance:the overpotential was 119 mV in 0.5 MH2SO4,43.9 mV in 1 MKOH,90.4 mV in 1 MPBS at the current density of 10mA cm-2,and the excellent OER performance in the alkaline environment(231 mV at 10mA cm-2).In addition,the addition of urea also significantly reduced the potential of anode reaction.When the electrolytic cell is assembled,the potential of urea-assisted electrolytic water is significantly lower than that of traditional electrolytic water,showing the advantage of urea-assisted water decomposition(2)self-supporting cross-intersected Ni1-yCoyO nanosheet coated CuOx nanotube electrode(CuOx@Ni1-uCoyO/CF)was successfully synthesized by in situ etching technique,solvent thermal deposition and heat treatment This three-dimensional nanotube@nanosheet hierarchical structure provides abundant active sites for catalytic reactions,and the three elemental compositions and heterostructures can improve the electronic structure and enhance the intrinsic catalytic activity of the catalyst.In addition,the in-situ growth of the active substance on the current collector increases the conductivity and promotes the charge transfer.Thanks to these advantages.the CuOx@Ni1-yCoyO/CF electrode demonstrated outstanding HER performance(46.9 mV at 10 mA cm-2)and HzOR performance(4.7 mV at 10 mA cm-2)in an alkaline environment Compared with OER potential(1.58 V at 10 mA cm-2),HzOR significantly reduced the potential of the anodic oxidation reaction(3)The cobalt phosphide quantum dots(CoP QD)were embedded in the metal organic framework(MOF)of nitrogen and phosphorus co-doped carbon(N,P-C)and grown directly on the nickel foam(CoP-QD@N,P-C/NF).The in-situ growth route without binder using can greatly improve the conductivity and avoid the aggregation of active substances.In addition,N,P-C can not only improve the conductivity,but also adjust the electronic structure to optimize the adsorption energy of the reaction intermediate Finally,CoP QD embedded in N,P-C skeletons can fully expose the active surface of electrocatalytic reaction,which greatly promotes the mass transfer of electrolyte.When the CoP-QD@N,P-C/NF electrodes were used as the cathode and anode of the full electrolyzer,the electrolyzer achieved ultra-efficient hydrogen production(4)the NiCoP of the micro-nano structure was obtained by simple chemical coordination,chemical etching and subsequent phosphorization treatment The NiCoP nanosheet coated micro-triangular structure provides strong support and a large surface area for prolonged circulation and sufficient electrolyte and electrode interface contact.Ni and Co not only promote catalytic performance,but also contribute to the increase of capacity with abundant valence states.NiCoP/NF showed excellent HER and HzOR performances,and the NiCoP/NF//Zn battery also showed excellent capacity behavior.Using solar cells,NiCoP/NF//Zn cells and NiCoP/NF//NiCoP/NF electrolytes constitute an uninterrupted and efficient hydrogen production system.During the day,solar power drives the production of hydrogen while charging NiCoP/NF//Zn batteries:At night,charged NiCoP/NF//Zn batteries provide high voltage for hydrogen production.