Hydrogen production via photoelectrochemical water-splitting is a key source of clean and sustainable energy. The use of one-dimensional nanostructures as photoelectrodes is desirable for photoelectrochemical water-splitting applications due to the ultralarge surface areas, lateral carrier extraction schemes, and superior light-harvesting capabilities. However, the unavoidable surface states of nanostructured materials create additional charge carrier trapping centers and energy barriers at the semiconductor-electrolyte interface, which severely reduce the solar-to-hydrogen conversion efficiency. In this work, we address the issue of surface states in GaN nanowire photoelectrodes by employing a simple and low-cost surface treatment method, which utilizes an organic thiol compound (i.e., 1,2-ethanedithiol). The surface-treated photocathode showed an enhanced photocurrent density of −31 mA/cm at −0.2 V versus RHE with an incident photon-to-current conversion efficiency of 18.3%, whereas untreated nanowires yielded only 8.1% efficiency. Furthermore, the surface passivation provides enhanced photoelectrochemical stability as surface-treated nanowires retained ∼80% of their initial photocurrent value and produced 8000 μmol of gas molecules over 55 h at acidic conditions (pH ∼ 0), whereas the untreated nanowires demonstrated only
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: KACST-TIC-R2-FP-008 J.H.H. greatly acknowledges the baseline funding from King Abdullah University of Science and Technology (KAUST) and the seed funds from the KAUST Solar Center. B.S.O. and T.K.N. acknowledge the financial support from King Abdulaziz City for Science and Technology (KACST), Grant KACSTTIC R2-FP-008. J.H.H. and V.P. sincerely thank Dr. Ahad Ali Syed and Dr. Xian Bin Wang of the Nanofabrication Core Laboratories, KAUST for their support with atomic layer deposition.