Abstract
Solar water splitting for hydrogen generation can be a potential source of renewable energy for the future. Here we show that efficient and stable stoichiometric dissociation of water into hydrogen and oxygen can be achieved under visible light by eradicating the potential barrier on nonpolar surfaces of indium gallium nitride nanowires through controlled p-type dopant incorporation. An apparent quantum efficiency of ∼12.3% is achieved for overall neutral (pH∼7.0) water splitting under visible light illumination (400-475 nm). Moreover, using a double-band p-type gallium nitride/indium gallium nitride nanowire heterostructure, we show a solar-to-hydrogen conversion efficiency of ∼1.8% under concentrated sunlight. The dominant effect of near-surface band structure in transforming the photocatalytic performance is elucidated. The stability and efficiency of this recyclable, wafer-level nanoscale metal-nitride photocatalyst in neutral water demonstrates their potential use for large-scale solar-fuel conversion.
Highlights
Solar water splitting for hydrogen generation can be a potential source of renewable energy for the future
Solar water splitting and hydrogen generation is an essential step of artificial photosynthesis for the direct conversion of solar energy into chemical fuels[1,2]
Among the currently known photocatalysts[6], group III-nitride semiconductors, for example, indium gallium nitride (InGaN) is the only material whose energy bandgap can be tuned across nearly the entire solar spectrum and can straddle water redox potentials under ultraviolet, visible and near-infrared light irradiation[7,8], thereby promising high efficiency overall water splitting under one-step photo-excitation
Summary
Solar water splitting for hydrogen generation can be a potential source of renewable energy for the future. Among the currently known photocatalysts[6], group III-nitride semiconductors, for example, indium gallium nitride (InGaN) is the only material whose energy bandgap can be tuned across nearly the entire solar spectrum and can straddle water redox potentials under ultraviolet, visible and near-infrared light irradiation[7,8], thereby promising high efficiency overall water splitting under one-step photo-excitation. Our recent study[21] suggests that by tuning the near-surface band bending on p-GaN nanowires, the quantum efficiency can be enhanced by nearly two orders of magnitude It has remained unknown whether the same concept can be extended into In-containing visible light active nitrides wherein tuning of the band bending has not yet been realized owing to increased strain, defects and In phase separation along with reduced over potential to straddle the redox potential. The p-type GaN/In0.2Ga0.8N nanowire photocatalyst exhibits a high level of stability
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