Cobalt Phosphate-Modified (GaN)1-x(ZnO)x/GaN Branched Nanowire Array Photoanodes for Enhanced Photoelectrochemical Performance

Photoelectrochemical water splitting based on suitable catalysts has attracted wide attention as a promising strategy to utilize solar energy to produce clean and renewable hydrogen fuel. Herein, we reported cobalt phosphate-modified (GaN)1-x(ZnO)x/GaN nanowire arrays on a high-temperature conductive GaN substrate toward enhanced photoelectrochemical water splitting by a facile two-step Au-assisted chemical vapor deposition method. The highly conductive Si-doped GaN substrate is designed to serve as a current collector and epitaxial substrate to grow GaN nanowires at high temperature. Meanwhile, high density of branched (GaN)1-x(ZnO)x nanowires with a tunable band gap, strong visible-light absorption, and high catalytic activity is deposited on the surface of GaN nanowires to act as active components to harvest light toward the oxygen evolution reaction. Such multi-junction heterostructures effectively enhance wide spectral utilization and light absorption and simultaneously accelerate the separation of electrons and holes and the transfer of photogenerated electrons from (GaN)1-x(ZnO)x nanowires to the GaN substrate collector and Pt electrode. The photocurrent density of the (GaN)1-x(ZnO)x/GaN nanowire array photoanode can reach 37.5 mu A cm-2 at 1.23 V vs reversible hydrogen electrode and could be further enhanced to 186 mu A cm-2 by modifying the cobalt phosphate cocatalyst, showing promising potential in clean hydrogen production.