Controllable Preparation And Electrocatalytic Performance Of Manganese Based Catalysts For Hydrogen Production

With the fast fossil fuel exhaustion and associated increasingly serious environmental pollution,it is very urgent to exploregreen and renewable energy resources in order to deal with this situation.Electrochemical hydrolysis of hydrogen is an environmentally friendly and sustainable technology.Hydrogen（H₂）with high energy density has been regarded as an ideal alternative energy carrierdue to its purity and sustain ability H₂ production by electrochemical water splitting in alkaline electrolyte which involves two half reactions,namely,the cathodic hydrogen evolution reaction（HER）and anodic oxygen evolution reaction（OER）.Unfortunately,traditional water electrolysis is subjected to the high energy consumption due to the sluggish kinetics of OER.Recently,the anodic small molecule oxidation reaction has been applied to solve the high energy consumption of traditional water electrolysis,in which the anodic OER is replaced with electrochemical oxidation of more favorably oxidized small molecules with low onset oxidation potential.Among these small molecule electrooxidation reactions boosted energy-saving water electrolysis techniques,anodic hydrazine electrooxidation reaction（Hz OR）boosted water electrolysis can sharply decrease the overall electrolysis voltage due to the ultra-low theoretical oxidation potential（-0.33 V vs reversible hydrogen electrode（RHE））of Hz OR.Based on the above problems,it is very important to design and prepare a stable,cheap and efficient HER/Hz OR dual-function catalyst suitable for electrocatalytic synthesis of hydrogen.In view of this,this article preparation is suitable for electric catalytic synthesis of hydrogen meter its HER/Hz OR double function of Mn-based catalyst,and the synthesis strategies of Mn-based catalysts are discussed in detail,studies the coupled electrochemical performance of anode Hz OR electric catalytic synthesis of hydrogen,further probes into the structure of the catalyst and the structure-activity relationship between electric catalytic properties,reveals the electrochemical reaction mechanism and regulation of law.The specific research contents are as follows:（1）Firstly,Mn-doped Co S₂ nanotube bi-functional electrocatalyst（Mn-COS₂）supported on nickel foam was prepared by hydrothermal sulfurization method,and excellent HER/Hz OR catalytic performance was obtained.The Mn-Co S2 catalyst only acquired a potential of 46 and 77 m V versus the reversible hydrogen electrode for achieving a current density of 10 m A cm^-2for cathodic HER and anodic Hz OR,respectively.The catalyst can maintain catalytic stability for up to 40 h.In addition,theoretical calculations show that Mn atom doping can adjust the electronic structure,so as to significantly reduce the Gibbs free energy of Co S₂ adsorption of H*,and accelerate the hydrazine oxidation reaction process in the rate-control step（dehydrogenation of*NH₂NH₂ to*NHNH₂）.（2）In addition,based on the inspiration of Mn-Co S₂ catalyst,further design and preparation a single atomic Mn site anchored on boron and nitrogen co-doped carbon nanotube array（Mn-SA/BNC）,and achieved better HER/Hz OR catalytic performance.The obtained catalyst achieves 51 m V overpotential at the current density of-10 m A cm^-2 for the cathodic HER and 132 m V versus the reversible hydrogen electrode for Hz OR,respectively.Besides,in a two-electrode overall hydrazine splitting（OHz S）system,the Mn-SA/BNC catalyst only needs a cell voltage of only 0.41 V to output 10m A cm^-2,with strong durability and nearly 100%Faradaic efficiency for H₂ production.In this paper,a HER/Hz OR dual-function Mn-based catalyst suitable for electrocatalytic synthesis of hydrogen was realized.At the same time,the catalytic reaction mechanism and influencing factors of catalytic performance were discussed in depth,which provided an important theoretical basis and important reference for low-cost and high-efficiency hydrogen production by electrolysis of water.