Synthesis of inexpensive hybrid nanomaterials for their application in photoelectrochemical water splitting

Abstract

The potential success of solar-to-fuels conversion relies upon the development of newlineefficient photocatalysts that can harvest greater range of photon energy from the solar newlineradiation to generate charge carriers, their efficient separation and faster transport to the newlinecatalytic active sites for hydrogen generation. Additionally, a suitable semiconductor newlinephotocatalyst requires a sufficiently negative conduction band edge (Ec) and positive newlinevalence band edge (Ev) to provide ample driving force to photo-generated electrons to newlinereduce H newline+ newlineinto H2 and photo-generated holes to oxidize water. The fast recombination newlineof photo-generated electrons and holes is one of dominant process in single band gap newlinesemiconductors that results in low IPCE and STH efficiency as the recombination newlineprocess (~10 newline-9 newlines) is much faster than surface redox reactions (10 newline-8 newline-10 newline-1 newlines). Therefore, the newlinesingle band gap semiconductor alone poses limitation and not competent enough for newlineoverall efficient solar to hydrogen generation. The formation of hetero-structured newlinephotocatalyst is highly desirable, which not only allows to harvest a broader range of newlinesolar radiation but also significantly promotes the separation of photo-generated charge newlinecarriers via hetero-interface, and thereby may improve solar-to-fuel conversion newlineefficiency. newlineThe potential of [111] oriented nano-columnar (ONC) and polycrystalline (PC) newlinethin films of Cu2O grown by oblique angle sputter deposition has been investigated for newlinevisible light driven water splitting reaction. As compared to PC-Cu2O, [111] ONCCu2O photocathode exhibits a significantly higher photocurrent density and IPCE (2 newlinefold). PC-Cu2O, requires relatively higher overpotential (34mV) than that of ONCCu2O for splitting of water. There is a relative decrease in the width of the space charge newlineregion (43 nm) and higher carrier density (5.06×10 newline22 newlinecm newline-3 newline) for ONC-Cu2O than those of newlinePC-Cu2O (82 nm and 4.38×10 newline22 newlinec