Preparation And Electro-catalytic Performance Of Transition Metal Phosphides And Chalcogenides For Water Splitting

The oxygen evolution reaction（OER）,and hydrogen evolution reaction（HER）are two pivotal reactions water splitting,which are usually drived by the large potential,because of their sluggish kinetics.The excellent catalysts are needed to reduce the activation energy barrier of the electrochemical process and accelerate the electrochemical reaction rate.Currently,Pt-,Ir-,and Ru-based materials are considered as the state-of-the-art electrocatalysts for HER and OER,but their high price and low reserves severely hinder the large-scale application of renewable energy technologies.Therefore,the synthesis of low-content noble metal-based and non-precious metal-based high efficient catalysts is considered to be an effective strategy for the realization of industrial water splitting.This paper main contents are as follows:（1）The rhodium and ruthenium salt are ultrasonically dispersed in phytic acid（carbon/phosphorus source）solution to obtain the metal complex precursors,which are pyrolyzed at high temperature under the mixture of Ar/NH₃ to form a composite catalyst,and it is composed of N and P co-doped nanocarbons and Rh_xP/NPC or RuP/NPC nanoparticles.For the two catalysts,the loadings of Rh and Ru are only 0.4 wt%and 0.5wt%,respectively.These catalysts exhibit excellent electrocatalytic performance for HER and OER because of synergistic effect of multiple active components,which are even better than those of state-of-the-art Pt/C and IrO₂.We also assembled water-splitting cells with Rh_xP/NPC and RuP/NPC catalysts,in which the potentials are only1.61 V and 1.64 V at the current density of 10 m A cm^-2,respectively.（2）MoS₂/NiS yolk–shell microspheres are successfully synthesized via a facile ionic liquid-assisted one-step hydrothermal method.With the favorable interface effect and hollow structure,the electrodes assembled with mixed sulfide MoS₂/NiS hybrid microspheres present remarkably enhanced electrochemical performance for overall water splitting.In particular,to deliver a current density of 10 m A cm^-2,the MoS₂/NiS||MoS₂/NiS cell for overall water splitting only needs an output voltage of 1.64 V in the alkaline medium,lower than that of Pt/C||IrO₂-based electrolysis cells（1.70 V）.In addition,as an electrode material for supercapacitors,it also shows excellent charge storage capacity and excellent rate performance.（3）Synthesize the precursor of nickel by hydrothermal method with reduced graphene as the substrate,and then prepare Fe,Al co-doped NiSe₂ nanoparticles（Fe,Al-NiSe₂/rGO）bifunctional electrocatalyst by a two-step synthesis method using selenium powder as selenium source.The Fe,Al heteroatoms are introduced into the NiSe₂ lattice to produce the strain effect,which improves the electronic interaction between the heteroatoms and the intrinsic atoms,optimizing the adsorption capacity of the intermediate product,and removing some Al atoms in the product expose more active sites.Finally,the OER overpotential of Fe,Al-Ni Se₂/rGO is only 272 mV at the current density of 10 mA cm^-2 and even exceeds IrO₂ of 293 mV.Compared with single ion doping and pure NiSe₂/rGO,electrocatalytic performance of both the HER and OER are significantly improved,and the assembled water splitting cell with the catalyst also exhibits excellent performance.