Photocatalytic water splitting using particulate semiconductors is a potentially scalable and economically feasible technology for converting solar energy into hydrogen. Z-scheme systems based on two-step photoexcitation of a hydrogen evolution photocatalyst (HEP) and an oxygen evolution photocatalyst (OEP) are suited to harvesting of sunlight because semiconductors with either water reduction or oxidation activity can be applied to the water splitting reaction. However, it is challenging to achieve efficient transfer of electrons between HEP and OEP particles. Here, we present photocatalyst sheets based on La- and Rh-codoped SrTiO3 (SrTiO3:La, Rh; ref. ) and Mo-doped BiVO4 (BiVO4:Mo) powders embedded into a gold (Au) layer. Enhancement of the electron relay by annealing and suppression of undesirable reactions through surface modification allow pure water (pH 6.8) splitting with a solar-to-hydrogen energy conversion efficiency of 1.1% and an apparent quantum yield of over 30% at 419 nm. The photocatalyst sheet design enables efficient and scalable water splitting using particulate semiconductors.

A vertically aligned Ta(3)N(5) nanorod photoelectrode is fabricated by through-mask anodization and nitridation for water splitting. The Ta(3)N(5) nanorods, working as photoanodes of a photoelectrochemical cell, yield a high photocurrent density of 3.8 mA cm(-2) at 1.23 V versus a reversible hydrogen electrode under AM 1.5G simulated sunlight and an incident photon-to-current conversion efficiency of 41.3% at 440 nm, one of the highest activities reported for photoanodes so far.

UV photoresponse of ZnO nanowires is measured in air under different humidity conditions to study the competitive surface effects of oxygen and water vapor. During UV illumination, it was found that the current decreases gradually under high humidity, whereas the current increases under low humidity. In the recovery phase, a change of two to three orders of magnitude in the decay time is observed by varying the humidity. A model that takes into account the solid-state process of photocarrier generation/recombination and the competitive surface effects of oxygen/water is proposed to explain the observed variations in photoresponse under different humidity conditions.

A nanowatt UV photoconductive detector made up of ultra-long (approximately 100 microm) ZnO bridging nanowires has been fabricated by a single-step chemical vapor deposition (CVD) process. The electrodes, forming comb-shaped thick ZnO layers, and the sensing elements, consisting of ZnO nanowires bridging the electrodes, were fabricated simultaneously in a single-step CVD process. The device showed drastic changes (10-10(5) times) in current under a wide range of UV irradiances (10(-8)-10(-2) W cm(-2)). Moreover, the detector exhibited fast response (rise and decay times of the order of 1 s) to UV illumination in air, but no response to visible light (hnu<3.2 eV). Our approach provides a simple and cost-effective way to fabricate high-performance 'visible-blind' UV detectors.