Sn2TiO4 Photoanodes for Near-Infrared Light-Driven Water Splitting with Ultralow Onset Potentials

Narrow band gap n-type semiconductors are attractive for high-efficiency solar hydrogen conversion via nonbiased photoelectrochemical (PEC) water splitting, but the high onset potentials of previously reported such materials remain an obstacle. Herein, we demonstrate for the first time that Sn2TiO4 photoanodes have a great potential to deal with this challenge by simultaneously exhibiting a low onset potential of ∼0.17 V versus reversible hydrogen electrode and near-infrared region (λ > 750 nm) PEC activity for water oxidation. We synthesized the Sn2TiO4 single-crystal particles with high crystallinity and prepared the electrodes by an improved particle-transfer method. Such an ultralow onset potential can be attributed to their negative flat band potential and high photovoltage. With an average particle diameter of ∼20 μm, their unique crystal structure, high crystallinity, and high carrier mobility still enable the charges to overcome the big particle sizes and the photoanode to exhibit noticeable photocurrent responses.