Study On Synthesis Of Pt-Ir Nanocrystals Substrated On Graphene And Its Electrocatalytic Performance

As the energy crisis become more and more serious,the needs for renewable and environmental-friendly energy become more urgent.Nowadays,electrochemical technologies have attracted much attention in the field of energy conversion and utilization because of its high efficiency,excellent selectivity and mild operating conditions.Among these,the technologies of hydrogen production from electrolytic water splitting and fuel cell have received extensive attention and research.However,the sluggish kinetics of oxygen evolution(OER)and oxygen reduction reactions(ORR)become the key to the development of these technologies.Therefore,to develop efficient electron-transfer multifunctional catalysts has become the research hot spots.In this work,a new catalyst of graphene supported Pt-Ir alloy was designed and synthesized by exploring the modified structure of substrate and active metals,which are expected to have good activity for OER and ORR.First,the faceted Pt-Ir nanocrystal was synthesized by seed-induced growth method.The octahedral Pt nanocrystals and icosahedral Pt nanocrystals were prepared in a hydrophobic system.The influences of the reductant amount,the injection temperature of reductant,addition method and the surfactant amount on the shape and aggregation extent of Pt nanocrsyta were investigated.In a hydrophilic system,cubic Pt nanocrystals and icosahedral Pt nanocrystals were synthesized.The influence of the surfactant amount on the shape and aggregation extent of Pt nanocrsyta was studied.Then the Pt-Ir nanocrystals were synthesized by injecting the as-synthesized Pt nanocrystal seed and Ir precursor at different temperature.The facet orientations of these as-synthesized nanocrystals were characterized by CV and physchemical methods.And the electrochemical activity for OER,ORR and HER of Pt and Pt-Ir nanocrystals were tested in acid solution.These nanocrystals exhibit excellent performance for OER,ORR and HER.Moreover,the substrate drived from silk was investigated.A facile method to prepare graphene-like carbon material from a natural silk fiber was developed by a potassium chloride intercalation and carbonization procedure.The K intercalation process and the influence of K intercalation on the porous structure of graphene-like carbon fiber were investigated by exploring the calcination temperatures.The high nanoporous structure on the surface facilitates fast ion transport and oxygen adsorption.Furthermore,the selective distribution of active N for ORR occurred in the process of K intercalation.Therefore,the obtained graphene-like cabonized silk fiber showed good ORR activity and high stability in acid solution.Finnally,a new composite electrocatalyst was synthesized by supporting the above Pt-Ir nanocrystal on the graphene-like carbon fiber.It was found that this composite electrocatalyst showed excellent electrochemical activity towards HER,OER and ORR.