A solar-responsive zinc oxide photoanode for solar-photon-harvester photoelectrochemical (PEC) cells

A highly efficient, nanostructured, solar-responsive zinc-oxide (SRZO) photoanode has been achieved by utilization of a versatile solution precursor plasma spray (SPPS) deposition technique. For the first time, it is demonstrated that a front-illumination type SRZO photo-anode fabricated with a ZnO/stainless steel (SS-304) configuration can generate an enhanced photo-electrochemical (PEC) current of 390 mA cm(-2), under solar radiation from a solar simulator with an AM1.5 global filter (similar to 1 sun). The SRZO electrode displayed a solar-to-hydrogen (STH) conversion efficiency of 2.32% when investigated for H-2 evolution in a PEC cell. These electrodes exhibited a maximum peak efficiency of 86% using 320 nm photons during incident photon-to-current conversion efficiency measurement. Interestingly, the film lattice of SRZO showed a significant red-shift of 0.37 eV in the ZnO band gap thereby providing solar photon absorptivity to SRZO. Further, an enhanced charge transport property by virtue of increased donor density (similar to 4.11 x 10(17) cm(-3)) has been observed, which is higher by an order of magnitude than that of its bulk counterpart. Efficient optical absorption of solar photons and higher donor-density of SRZO have been thus attributed to its superior PEC performance.