Controllable Construction Of Transition Metal Ni, Co Phosphide Nanocrystals And Their Electrocatalytic Propertie

Nowadays,with the increasing global demand for energy and the growing crisis of living environment,it becomes urgent to develop clean and renewable energy sources.Electrochemical decomposition of water is one of the efficient ways to produce hydrogen,and the selection of a suitable catalyst is crucial.Transition metal phosphides have become a focus of attention due to their platinum-like catalytic activity.In this paper,transition metal phosphides are used as the main body,and the electronic structure is regulated by compounding them with carbon materials and doping them with heteroatoms to optimize the adsorption of intermediates in the electrocatalytic process,which in turn enhances the electrocatalytic activity.Among the non-precious metal-based electrocatalysts,Ni2P is considered as a promising candidate due to its high catalytic activity,better chemical stability,and excellent electrical conductivity.The nanocomposites were prepared by in situ growth of monodisperse Ni2P nanocrystals onto rGO using inexpensive,stable and less toxic precursors via the Schlenk technique.Ni2P nanocrystals with an average size of 5 nm are uniformly dispersed inside and on the surface of the rGO.The excellent electrical conductivity and interconnected porous network of rGO provide a large number of active sites for electrocatalytic reaction processes.The overpotential of Ni2P nanocrystals was 182 mV under alkaline conditions when the current density was 10 mA cm-2 and as low as 143 mV for Ni2P/rGO nanocomposites.Meanwhile,Ni2P/rGO also shows better Li-ion battery characteristics,including long-life cycle stability(Capacity can be maintained at 389.9 mAh g-1 after 1000 cycles at 1 C)and high multiplicity capability(Capacity can be maintained at 197.7 mAh g-1 at 50 C).In addition,the Co2P nanorods with a size of about 90 nm were synthesized by the same preparation method,and Fe-Co2P with different morphologies could be formed by adjusting the amount of Fe doping.There is an optimal value of Fe doping,and excessive or small amount of doping can affect the performance of the catalysts.Among these catalysts,Fe-Co2P exhibited the best HER activity when the Co:Fe molar ratio was 1:0.2,driving a current density of 10 mA cm-2 with an overpotential of 91 mV and 141 mV in alkaline and acidic electrolytes,respectively.The doping of Fe atoms increased the electrical conductivity of Co2P,which facilitated the rapid transfer of electrons and improved the efficiency of active site utilization.The donor-acceptor behavior of electrons was regulated thus optimizing the adsorption performance of the relevant intermediates.In addition,the morphology of Fe-Co2P split nanorod bundles facilitated the diffusion of water and hydrogen release,exposing a large number of active sites and thus exhibiting good electrocatalytic activity.