Synthesis and Structure of an Ion-Exchanged SrTiO3 Photocatalyst with Improved Reactivity for Hydrogen Evolution

Abstract

BaTiO3 heated in an excess of SrCl2 at 1150 °C converts to SrTiO3 through an ion exchange reaction. The SrTiO3 synthesized by ion exchange produces hydrogen from pH 7 water at a rate more than twice that of conventional SrTiO3 treated identically. The apparent quantum yield for hydrogen production in pure water of the ion exchanged SrTiO3 is 11.4% under 380 nm illumination. The catalyst resulting from ion-exchange differs from conventional SrTiO3 by having ≈2% residual Ba, inhomogeneous Cl-doping at a concentration less than 1%, Kirkendall voids in the centers of particles that result from the unequal rates of Sr and Ba diffusion together with the transport of Ti and O, and nanoscale regions near the surface that have lattice spacings consistent with the Sr-excess phase Sr2TiO4. The increased photochemical efficiency of this nonequilibrium structure is most likely related to the Sr-excess, which is known to compensate donor defects that can act as charge traps and recombination centers.