Recent progress in the development of (oxy)nitride photocatalysts for water splitting under visible-light irradiation

Hydrogen is considered to be a clean energy carrier alternative to exhaustible resources such as fossil fuels. To facilitate the transition to a hydrogen economy, hydrogen production using renewable energy is an important focus of attention. Splitting water into hydrogen and oxygen using a photocatalyst and sunlight is a potential candidate for future hydrogen production. To utilize sunlight efficiently, photocatalysts must be responsive to visible light with longer wavelengths, which makes up the majority of sunlight. Among transition metal (oxy)nitrides with d(0)-electronic configurations, there are some photocatalysts with the potential to split water by absorbing light with wavelengths up to similar to 600 nm. However, overall water splitting has not yet been achieved by these 600 nm-class photocatalysts. It is very likely that defects in photocatalysts that are inevitably formed during conventional preparation processes degrade their photocatalytic performance. In this review, we provide a summary of recent progress in the development of visible-light-responsive (oxy)nitride photocatalysts, especially from the aspect of syntheses and post-treatments to obtain high-quality crystals with few defects. (C) 2013 Elsevier B.V. All rights reserved.