A quadruple-band metal-nitride nanowire artificial photosynthesis system for high efficiency photocatalytic overall solar water splitting

Photocatalytic water splitting is a wireless method for solar-to-hydrogen conversion. To date, however, the efficiency of photocatalytic water splitting is still very low. Here, we have investigated the design, synthesis, and characterization of quadruple-band InGaN nanowire arrays, which consist of In0.35Ga0.65N, In0.27Ga0.73N, In0.20Ga0.80N, and GaN segments, with energy bandgaps of similar to 2.1 eV, 2.4 eV, 2.6 eV, and 3.4 eV, respectively. Such multi-band InGaN nanowire arrays are integrated directly on a nonplanar wafer for enhanced light absorption. Moreover, a doping gradient is introduced along the lateral dimension of the nanowires, which forms a built-in electric field and promotes efficient charge carrier separation and extraction for water redox reactions. We have demonstrated that the quadruple-band InGaN nanowire photocatalyst can exhibit a solar-to-hydrogen efficiency of similar to 5.2% with relatively stable operation. This work demonstrates a novel strategy using multi-band semiconductor nanostructures for artificial photosynthesis and solar fuel conversion with significantly improved performance.