Design And Preparation Of Nano-electrocatalyst Based On Transition Metal Materials

In recent years,with the requirements for building a resource-saving and environment-friendly society,as well as the recent launch of carbon peak and carbon neutral timetables,all have shown the necessity of research and development of next-generation energy and storage equipment.In energy production and storage devices,electrocatalysts are one of its key components.It is generally believed that noble metal catalysts are ideal electrocatalyst materials,but their scarcity and high cost limit the wide application of noble metal catalysts.A lot of work has been devoted to the development of catalytic materials that can replace precious metals.In this work,the design and preparation of nano-electrocatalyst based on transition metal materials are studied,and the following two tasks are done:(1)In the present work,an efficient four-step strategy to fabricate the Fe-Co-P porous nanowire arrays in situ grown on a self-supported carbon cloth(denoted as Fe-Co-P/CC)for developing excellent hydrogen evolution reaction(HER)activity is reported.The four steps include the preparation of the CoFeZn-precursor by a hydrothermal reaction,the formation of pore-forming agent(ZnO)after annealing treatment,the alkaline etching of ZnO and phosphorization.Particularly,the alkaline-etched porous Fe-Co-P nanowire-arrays contribute to enhancing the catalytic activity by the exposure of more electrochemical active sites.The as-prepared Fe-Co-P/CC which was prepared by the rational Co-Fe molar ratio,as a binder-free electrocatalyst,shows a high-performance HER with a small overpotential of 121 mV in 1 M KOH and 124 mV in 0.5 M H2SO4 at a current density of 10 mA·cm-2,as well as a good Tafel slope value of 118 mV/dec and 85 mV/dec in alkaline and acid media,respectively,owing to the well optimized pore-structures and active sites.Additionally,the catalyst almost maintains its electrochemical activity for about 24 and 16 hours under alkaline and acidic conditions,respectively.This work provides a new idea for the synthesis of high-efficiency,binder-free electrodes for high-purity hydrogen production.(2)It is extremely crucial for the commercial application of zinc-air batteries to explore economical,efficient and stable non-precious metal oxygen reduction reaction(ORR)electrocatalysts to replace the precious metal platinum.Herein,a method of modification by polyethyleneimine(PEI)is used to fabricate N and S co-doped iron-containing three-dimensional porous carbon materials(defined as cal-FeZIF-NSC).This process is mainly divided into five steps,namely,mechanical grinding to prepare precursor,calcination and etching to form porous carbon structure,PEI modified carbon material,coordination with transition metal to form ZnFePEI-NSC precursor and calcined zeolite imidazole ester framework structure material(Zeolitic Imidazolate Frameworks,ZIF)finally formed cal-FeZIF-NSC composite material.Benefiting from the coordination of transition metal ions and amine groups,there is no metal aggregation in the final cal-FeZIF-NSC composite.Instead,the transition metal Fe may be uniformly distributed in the catalyst at the atomic level.The prepared cal-FeZIF-NSC catalyst exhibited good ORR catalytic activity,good half-wave potential,and no significant attenuation of the overpotential after the 10,000-cycle cyclic voltammetry test.These results can be attributed to the fact that the tiny metal Fe is evenly dispersed in the catalyst,on the other hand,the preparation of heteroatom-doped three-dimensional porous interconnected carbon materials,so its structure is not only conducive to the transfer of charges at the interface as well as the transmission of electrons,but also facilitates the transportation of ORR-related substances and exposes more catalytically active sites during electrochemical reactions.At the same time,the doping of N,S and other heteroatoms improves the conductivity of carbon materials.And the optimization of the electronic structure has played a certain role in improving the performance of cal-FeZIF-NSC electrocatalyst.In addition,the prepared cal-FeZIF-NSC composite material was further assembled into a zinc-air battery,demonstrating the huge application potential of the catalyst in the field of energy storage.Figure 41 table 5 reference 150.