Study On Preparation And Performance Of Mo Based Electrocatalyst For Hydrogen Evolution And Mg Seawater Batteries

Electrocatalytic water splitting can convert electric energy into chemical energy and store it in clean energy carrier hydrogen.It is an effective way to solve the increasingly serious global environmental pollution problem and energy crisis.At present,platinum based materials are the best choice for water splitting to produce hydrogen.However,their scarce resources and high price seriously restrict their large-scale industrial application.Therefore,the development of efficient and cheap electrocatalysts to replace expensive platinum based materials is the research focus and hotspot in the field of electrocatalytic hydrogen production.Recently,molybdenum based materials have attracted extensive attention and research in the field of electrocatalytic hydrogen production due to their characteristics of rich reserves,diverse crystal structures and excellent physical and chemical properties.However,compared with precious metal platinum based materials,the electrocatalytic hydrogen production activity of molybdenum based materials is far from meeting the needs of commercial applications.Therefore,how to improve the electrocatalytic hydrogen evolution activity of molybdenum based materials is a challenge in the process of catalyst design and preparation.To this end,this paper focuses on the design,preparation and electrocatalytic hydrogen evolution performance of high-efficiency molybdenum based catalysts.The main research contents and conclusions are as follows:Nickel doped molybdenum trioxide nanosheets（Ni-MoO₃）were designed and synthesized with Anderson type heteropoly acid（NH₄）₃[NiMo₆O₁₈（OH）₆]·7H₂O（NiMo₆）as precursor for the first time.Nickel doped molybdenum dioxide nanosheets（Ni-MoO₂）were obtained by phase transformation engineering,and then the effect of phase transformation on the electrocatalytic hydrogen evolution activity of nickel doped molybdenum oxide was studied.The results show that the overpotential of initial Ni-MoO₃nanosheets to gain 10 m A cm^-2current density in acid,alkali and seawater electrolyte is as high as 326,493 and 818 m V,respectively,while the overpotential of Ni-MoO₂nanosheets to gain 10 m A cm^-2current density in acid,alkali and seawater electrolyte is reduced to 200,234 and 412 m V,respectively,indicating phase change engineering can greatly improve the intrinsic electrocatalytic hydrogen evolution activity of nickel doped molybdenum oxide.Meanwhile,when Ni-MoO₂nanosheets was used as the hydrogen evolution cathode in Mg/seawater battery,the maximum power density of the assembled battery is 6.54 m W·cm^-2,indicating that it has potential application in Mg/seawater battery.Rare earth element Er was introduced into MoO₂through hydrothermal synthesis process,and a bifunctional catalyst（Er-MoO₂）for overall water splitting was successfully constructed.Thanks to the effective regulation of the electronic structure of MoO₂by Er element,the hydrogen evolution（HER）and oxygen evolution（OER）overpotentials of Er-MoO₂at 10 m A cm^-2current density in alkaline environment are only 94 m V and 245 m V,respectively.In simulated seawater（3.5%Na Cl）,the HER and OER overpotentials of Er-MoO₂at 10 m A cm^-2current density are only 173 m V and 312 m V respectively,which also exhibits a long-term stability of continuous electrolysis up to 24 h.When used as a bifunctional catalyst for electrocatalytic overall water splitting,Er-MoO₂can obtain a current density of 100 m A cm^-2only at a call voltage of 1.90 and 2.03 V in alkaline and alkaline seawater environment,respectively,which surpass state-of-the-art non noble metal based catalysts.In addition,a Mg/seawater battery prepared with Er-MoO₂as hydrogen evolution cathode shows excellent discharge performance,and the peak power density reaches 8.17 m W cm^-2,which is close to the Mg/seawater battery based on commercial Pt/C hydrogen evolution cathode.Further more,a battery pack assembled based on the Mg/seawater battery is able to light up a LED panel,indicating its potential application in practical.