High-efficiency photoelectrochemical hydrogen generation enabled by p-type semiconductor nanoparticle-decorated n-type nanotube arrays

Abstract

TiO₂ nanotube arrays (TNTAs) were decorated with NiO nanoparticles via a sequential chemical bath deposition (CBD) approach to yield NiO@TNTA photoanodes. In sharp contrast to pure TNTAs, NiO@TNTAs displayed increased absorption and decreased photoluminescence. Interestingly, NiO@TNTA photoanodes exhibited a higher photoelectrochemical activity for hydrogen production than pure TNTAs. The incident-photon-to-current-conversion efficiency (IPCE) of the optimized NiO@TNTA photoanode was calculated to be 62.8%, and remarkably, the maximum hydrogen production rate reached 37.8 μmol h⁻¹ cm⁻², approximately 5.0 times faster than pure TNTAs. Such markedly enhanced photoelectrochemical efficiency can be attributed primarily to the efficient separation of photogenerated charge carriers at the p–n junction of the two dissimilar semiconductors, that is, p-type NiO and n-type TiO₂, in conjunction with the implementation of nanosized NiO particles with large surface area which enables a shortened charge transfer distance and in turn increased probability of reaction of charge carriers with water molecules.