Controlled Preparation Of High-efficiency Transition Metal-based Electrocatalysts

Mass consumption of traditional fossil fuels has caused serious climate and environmental problems,and improved cleanliness and the use of renewable energy sources and technologies are imminent.Among the various energy sources,hydrogen energy has attracted more and more attention due to its high energy density and no carbon emissions.Therefore,electrochemical water splitting technology is considered a promising technology for producing clean and sustainable hydrogen fuel.Electrochemical water splitting involves two main half reactions:oxygen evolution and hydrogen evolution.However,both of these reactions require a catalyst to increase efficiency.The transition metal ruthenium has an unsatisfactory electron arrangement structure,which is conducive to the formation of adsorption bonds,so that it exhibits good hydrogen evolution performance,and it has attracted widespread attention because of its similar electronic structure to Pt.Moreover,Ru is much cheaper than Pt,has stronger corrosion resistance and higher catalytic activity.Based on the above advantages,this paper prepared three kinds of transition metal ruthenium-loaded heteroatom-doped carbon materials,using scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（Characterization methods such as XPS）and Raman spectroscopy（Raman）analyze the morphology and structure of the prepared materials,using cyclic voltammetry（CV）,linear sweep voltammetry（LSV）,and chronoamperometry（it）and accelerated durability test（ADT）and other test methods to study the electrocatalytic performance of the prepared catalyst,and obtained many meaningful results,which are summarized as follows:1.The Ru/B,N-CNTs-T（where T stands for the pyrolysis temperature）composite materials are successfully prepared by a simple solution mixing method,followed by pyrolysis at different temperatures,to load Ru on B,N-doped carbon nanotubes（CNTs）.In alkaline media,the as-obtained composite materials have high catalytic activity for both hydrogen evolution and oxygen evolution reaction.Among them,the prepared Ru/B,N-CNTs-600 catalyst exhibits best electrocatalytic performance.For the hydrogen evolution reaction and oxygen evolution reaction,the optimized catalyst only needs overpotentials of 54 m V and 333 m V to achieve a current density of 10 m A cm^-2.At the same time,the water electrolysis device assembled with Ru/B,N-CNTs-600/NF as anode and cathode,respectively,can drive all the water splitting to the current density of10 m A cm^-2 at a voltage of 1.57 V,and has a long-term stability.2.The solvothermal synthesis method is used to coordinate p-phenylenediamine with Ru and form a coordination polymer with formaldehyde.After pyrolysis,the Ru/NC-T（where T represents the pyrolysis temperature）composite materials are obtained.The catalyst has excellent electrocatalytic activity for HER.The optimized Ru/NC-800 catalyst has an overpotential of 10 m V at a current density of 10 m A cm^-2 and a smaller Tafel slope than Pt/C.3.Using dicyandiamide as a nitrogen source,nitrogen-containing glucose microspheres are synthesized by a hydrothermal method.The adsorption of Ru on the nitrogen-containing glucose microspheres by a solution impregnation method and subsequent pyrolysis treatment of the obtained product lead to Ru-loaded N-doped carbon microspheres composite materials,named Ru/NCS-T（where T stands for pyrolysis temperature）.The as-prepared Ru/NCS-800 catalyst has excellent catalytic activity for hydrogen evolution reaction.It only requires an overpotential of 30 m V to reach the current density of 10 m A cm^-2,and has excellent durability and stability.