Rational Design Of Novel Transition Metal- And Platinum Group-based Electrocatalysts

Since the third industrial revolution,the human society are developing rapidly with extremely fast energy consumption.Entering the 21^st century,the energy problem has become one of the biggest problems that trouble the human society.Currently,the traditional fossil fuels are still the main energy sources,which has caused many environmental and energy problems.Therefore,developing sustainable energy sources play an important role in replacing fossil fuels.Using electrochemical process to convert electric energy into chemical energy is a promising sustainable energy utilization.Therefore,this work focuses on developing novel electrocatalysts,which efficiently convert electric energy into hydrogen or fuel cells,or convert CO2 into valuable chemicals.Meanwhile,among the many kinds of electrocatalysts,this work focuses on catalysts based on transition metal-and platinum group-based composites.We first developed a novel‘low-temperature sulfidation’method to prepare 1D MO2（M=W,Mo）nanorods（NRs）.As a result,loosely stacked few-layered MS2nanosheets were formed on the nanorod surface and acted as active sites for HER.Meanwhile,the 1D MS2/MO2 NRs inherit the porous and conductive properties from their metallic dioxides.Hence,the MS2/MO2 NRs exhibit excellent activities and stabilities for HER,which significantly outperform their corresponding bulk dichalcogenides and dioxides.This work also provides a new perspective for fabricating transition-metal sulfides or other compounds with specific nanostructures from their corresponding metallic dioxides precursors.We then developed novel wide-p H HER electrocatalysts based on transition metal phosphides（TMPs）.In this work,transition metals（Mo and Co）have been doped into pristine WP,leading to the formation of novel porous M-WP（M=Mo,Co）nanomaterials.The as-prepared M-WP nanomaterials exhibit numerous advantages:higher surface areas,more porous nanostructures,more exposed active sites and lower resistance for charge transfer.DFT calculations demonstrate that the Co dopants synergistically enhance the water dissociation rate and optimize hydrogen adsorption free energy during the entire HER process.Consequently,the Co-WP catalyst exhibits efficient HER activity and stability over wide p H range.Then we developed an L-phenylalanine（LPHE）-templated fabrication of Pt-AL/C nanomaterial with the assistance of room-temperature electron reduction.Loading Pt-LPHE onto carbon support produces a Pt-AL/C nanomaterial with highly dispersed Pt NPs.Our density functional theory（DFT）results demonstrate that Pt NPs bind more strongly on Pt-AL/C with pyrrolic/pyridinic-N,which contributes to stabilizing Pt NPs in the catalyst.Meanwhile,the*O/*OH binding energies are weaker on Pt-AL/C than on pure Pt NPs and Pt/C.As a result,the mass activity（MA）and specific activity（SA）of Pt-AL/C are higher than commercial Pt/C,respectively.Moreover,this work provides a new perspective for using inexpensive biological components as templates to prepare Pt group metal NPs with controllable facets and sizes.Finally,we prepared transition metal carbides（TMCs,i.e.Ta C and Nb C）using a hard template method.Pd nanoparticles were then loaded onto TMC substrates.Compared with other catalysts,Pd/Ta C exhibited the higher CO2RR activity and CO Faradaic efficiency,and the gas product was syngas.Moreover,the Pd usage of Pd/Ta C was significantly reduced.In-situ characterizations confirmed that the Pd was transformed to Pd H during CO2RR.DFT calculations demonstrate that the TMC substrates affected the CO2RR via adjusting the formation of*HOCO on Pd H.This work extends the applications of TMCs in the electrocatalysis,and demonstrates the effect of TMCs on the activity of CO2RR.