Systematic material study reveals TiNb2O7 as a model wide‐bandgap photoanode material for light‐assisted solar water splitting.

Our work reveals that TiNb2O7 (TNO) powder-based photoanodes demonstrate remarkable water oxidation properties - composed of nearly ideal charge transfer and charge injection efficiencies. Furthermore, our simplified photoanode construction and careful survey of structural and morphological characteristics, using oriented and polycrystalline thin films and powder-based samples, indicate that TNO water splitting kinetics is negligibly effected by surface morphology; rather, internal grain boundaries likely play a driving role. Our TNO powder-based photoanodes exhibit ideal water oxidation kinetics and oxidize water at minimal applied biases while under illumination; consequently, it exhibits an early onset photocurrent voltage (0.4V vs RHE) which rivals that of other state-of-the-art photoanode materials.