Carrier Pathway for Photoelectrochemical Water Oxidation with Intermediate State in n-type GaN Compared with Route of Anodic Corrosion

Abstract

Photoelectrochemical water splitting is a solar-to-chemical energy conversion technique. However, when n-type nonoxide semiconductors are used as photoanodes, they corrode, which is a competitive reaction with water oxidation. To evaluate these competing reactions, the optical properties (photoluminescence) of n-type GaN were examined and compared with the results of a photoelectrochemical analysis. The intermediate hole trap state associated with the yellow luminescence of GaN was found to be a candidate for the carrier transfer site for water oxidation. The hole for electrode corrosion was estimated to have a different pathway from this trap site and to be associated with the hole located at the valence band edge.

Achieving Record-High Photoelectrochemical Photoresponse Characteristics by Employing Co3O4 Nanoclusters as Hole Charging Layer for Underwater Optical Communication

“…However, the large surface-to-volume ratio of the III–V nanowires becomes a double-edged sword in the pursuit of advanced devices for practical application . On one hand, the nanowire configuration with a large surface area would give them superior sensitivity to the surroundings, compared with their bulk counterparts, but once they are exposed to an air or liquid environment, it causes surface oxidation, chemical corrosion, or photocorrosion with severe material degradation, leading to poor device performance . Additionally, the large surface area also leads to the presence of a high density of surface states which could act as carrier nonradiative recombination centers or introduce a pinned Fermi level that hinders the realization of highly efficient nanophotonics and electronics .…”

“…8 On one hand, the nanowire configuration with a large surface area would give them superior sensitivity to the surroundings, compared with their bulk counterparts, but once they are exposed to an air or liquid environment, it causes surface oxidation, chemical corrosion, or photocorrosion with severe material degradation, leading to poor device performance. 9 Additionally, the large surface area also leads to the presence of a high density of surface states which could act as carrier nonradiative recombination centers or introduce a pinned Fermi level that hinders the realization of highly efficient nanophotonics and electronics. 10 On the other hand, the extraordinarily high surface-to-volume ratio of these nanowires with extensively exposed surface atoms endow such lowdimensional nanowires with large contact areas for active sites, for instance, in photoelectrochemical (PEC) applications, and also provide an efficient approach for nanowire surface reconstruction by implementing heterostructures to enhance nanodevice performance.…”