Nickel Phosphide And Cobalt Phosphide As The Cocatalyst For Photocatalytic Hydrogen Production And Photoelectrochemical Water Splitting

Photocatalytic hydrogen(H2)evolution and photoelectrochemical(PEC)water splitting are promising approaches for future sustainable energy utilization.Traditionally,noble metals and their oxides(such as Pt,Ru,and IrO2)are regarded as the best cocatalysts for photocatalytic H2 evolution and PEC water splitting when integrated with a semiconductor.However,their high costs make them less attractive for practical applications.Thus,it is extremely important to explore cheap and non-noble metal cocatalysts suitable for photocatalytic water splitting into hydrogen and PEC water splitting.Metal-free graphene quantum dot(GQD)is a promising metal-free photocatalyst because of its good water-solubility,tunable band gap,and facile synthesis procedure.On the other hand,metal phosphides(Ni2P,Co2P,etc)have been demonstrated as novel noble-metal-free cocatalysts for water splitting,which can efficiently separate electron-hole pairs and enhance the photocatalytic activities.In this thesis,we report for the first time on the use of OH-functionalized GQDs(OH-GQDs)photosensitizer coupled with Ni2P nanoparticles(NPs)for photocatalyic H2 production under visible light(?>420 nm).The catalytic activity is?94 times higher than that of bare OH-GQDs,which is even comparable to that of OH-GQDs with 1 wt%Pt cocatalyst.Recently,Co-based cocatalysts have attracted a wide range of research interests to improve the performance of photoanodes for PEC water splitting owing to their low catalytic overpotentials for water oxidation.In this thesis,we report CoP as an efficient cocatalyst to couple with WO3 photoanode using a simple drop-casting method.With cocatalyst loading,the composite photoanode showed better PEC performance owing to the increasing hole injection efficiency.Under optimal conditions,a current density of CoP/WO3 up to 1.2 mA cm-2 at 1.23 V vs.RHE and 80 mV cathodic shift of onset potential can be obtained,indicating that CoP is an efficient cocatalyst for photoelectronchemical water oxidation.