Investigation Electrochemical Performance Of Transition-metal Dichalcogenides

With the rapid and efficient development of the global economy,the demand for fossil energy is increasing significantly.However,the formation of non-renewable fossil fuels takes a long time.In this situation that demand is much greater than supply caused severely energy crisis.At the same time,the environmental problems are caused by greenhouse gases such as carbon dioxide and harmful gases such as carbon monoxide generated by fossil energy during the combustion process.At the same time,poisonous gas,such as carbon dioxide and carbon monoxide,produced by fossil fuels during combustion,have been caused increasingly serious environmental problems.Therefore,the development of clean,environmentally friendly,renewable resources is actually very urgent.First,hydrogen is abundant on earth and mainly exists in water in combing state.Secondly,the heat generation,thermal conductivity and combustion of hydrogen are good.Finally,hydrogen is non-toxic and recyclable resource.The technology that production of hydrogen using electrocatalytic water splitting plays an vital role in the field of energy storage and transformation,and also can be widely used in military,aerospace,new energy electric vehicles and other fields.However,the key factor affecting the performance of electrolytic water is the electrode catalyst.according to the analyze above,in this paper,the strategy of nanostructure design,carbon cladding,anion doping,etc.,optimizes the shape,composition,conductivity,surface area of the material,and the binding strength of catalyst and adsorption to increase the activity of the catalyst in essence.Nickel disulfide（Ni S₂）and nickel diselenide（Ni Se₂）are regarded as potential materials to substitute the noble metal catalysts for both HER and OER due to its unique optical,electrical,and magnetic characteristics.Nevertheless,the electrocatalytic properties of them are still limited by its unsatisfactory electronic conductivity,durability and inherent activity.Here,we report a series of flower-like electrocatalysts with Ni(S_xSe_1-x)₂ nanoparticles encapsulated by porous graphitized carbon nanosheets（PGCNS）,and reveal ultra-sensitive S/Se species-induced behaviors.By virtue of anion doping and the unique architecture,Ni(S_xSe_1-x)₂@PGCNS samples show enhanced activity for both HER and OER in alkaline conditions.This work highlights these progresses that it rivals with the reported catalysts from the following aspects,including controllable component,ultra-sensitive S/Se species-induced behaviors,flower-like PGCNS structure and remarkably performance for overall water splitting in alkaline media.（1）A series of flower-like Ni(S_xSe_1-x)₂@PGCNS composites are synthesized by combination of anion doping and unique structure.More importantly,our synthesis strategy can be used to fabricate other high-efficiency metal-based sulfoselenide electrocatalysts for various application in energy conversion.（2）The positive effects of S/Se species are explored by novel function theory（DFT）calculations,suggesting that d band center and the electrochemical performance of catalyst for HER and OER are modified through introducing S or Se.（3）The porous graphitized carbon nanosheet to encapsulate Ni(S_xSe_1-x)₂ particles not only increases specific surface areas but also enhances stability and conductivity.（4）Combined merit of the most rational doping and unique architecture,Ni(S_0.61Se_0.39)₂@PGCNS reveals the highest performance for HER(η₁₀=62.7 mV vs RHE and a Tafel slope of 62.0 mV dec^-1)and Ni(S_0.24Se_0.76)₂@PGCNS shows the best activity for the OER(η₁₀=202.9 mV vs RHE and a Tafel slope of 41.6 mV dec^-1).A two-electrode water electrolyzer using Ni(S_0.61Se_0.39)₂@PGCNS as the cathode and Ni(S_0.24Se_0.76)₂@PGCN as the anode requires voltage of 1.54 V at 10 m A cm^-2 and exhibits excellent stability at current density of 10,30 and 50 m A cm^-2 in alkaline.The superb performance of water splitting under alkaline media demonstrates Ni(S_0.61Se_0.39)₂@PGCNS and Ni(S_0.24Se_0.76)₂@PGCN are promising catalysts to substitute commercial IrO₂ and Pt/C.