InGaN/Cu2O Heterostructure Core-Shell Nanowire Photoanode for Efficient Solar Water Splitting

Abstract

The heterostructuring and doping concepts have proved to obtain a novel n-InGaN/p-Cu2O nanowire (NW) photoanode by strong enhancement of the photocurrent compared to a bare InGaN NW photoanode in solar water splitting. The large photocurrent is due to the maximized photocarrier separation and hole transfer to the surface in the depletion zone of the p–n heterojunction established by the p-Cu2O layer, forming a thin, uniform shell-layer around the n-InGaN NW core by electrodeposition. For sufficiently thin Cu2O layers, the upward energy band bending in the depletion zone extends up to the surface for optimized hole transport and surface reaction. Thick Cu2O layers on top of the InGaN NWs act as common photocathodes. The functional InGaN/Cu2O heterostructure core-shell NW photoanode is chemically self-stabilized at positive applied voltage by a thin CuO surface layer. Final deposition of the earth-abundant NiOOH co-catalyst boosts the photocurrent of the InGaN/Cu2O/NiOOH complete NW photoanode into the competitive mA/cm2 range.

Enhanced Light Trapping and Charge Separation via Pyramidal Cu2O/NiCo-LDH Photocathode for Efficient Water Splitting

“…The electrodeposition time was 150 s. The loading amount of the Cu 2 O layer vs electrodeposition time on the ITO and Si/InGaN substrate, including the effect of loading amount on PEC and electronic performance, has been studied in our previous publications. 36,37 2.5. Electrodeposition of NiCo-LDH Cocatalyst.…”

“…The deposition temperature was set to 45 °C in the solution with magnetic stirring of 180 rpm. The electrodeposition time was 150 s. The loading amount of the Cu 2 O layer vs electrodeposition time on the ITO and Si/InGaN substrate, including the effect of loading amount on PEC and electronic performance, has been studied in our previous publications. , …”

Planar GaN/Cu2O Microcrystal Composite Junction Photoanode for Efficient Solar Water Splitting

“…For thicker p-type layers, the near-surface upward energy band bending will diminish and eventually reverse to a near-surface downward energy band bending for thick, bulk p-type layers. The photocurrent passes a maximum, then decreases, and finally becomes negative . This is the transition and final formation of the familiar thick p-type semiconductor photocathode, which is deeply studied for thick p-Cu 2 O layers with near-surface downward energy band bending and a negative photocurrent.…”

“…The p-Cu 2 O microcrystals exploited here with limited height are electrodeposited on the planar n-GaN layers grown by plasma-assisted molecular beam epitaxy (PA-MBE) on p-Si (111) substrates to produce the composite junction photoanode for enhanced solar water splitting. Cu 2 O is a p-type semiconductor due to Cu vacancies with a bandgap energy of 2.1 eV and has been previously exploited for this and other purposes on InGaN and GaN nanowires. , On planar GaN layers, compared to nanowires, however, there are no geometrical constraints for the deposition of Cu 2 O, such as the nanowire separation, and the access of the surface by the electrolyte is free and basically unlimited with minimized reactant depletion. Furthermore, Cu 2 O is nontoxic and Cu is a common element on earth.…”

“…Cu 2 O is a p-type semiconductor due to Cu vacancies with a bandgap energy of 2.1 eV and has been previously exploited for this and other purposes on InGaN and GaN nanowires. 28,29 On planar GaN layers, compared to nanowires, however, there are no geometrical constraints for the deposition of Cu 2 O, such as the nanowire separation, and the access of the surface by the electrolyte is free and basically unlimited with minimized reactant depletion. Furthermore, Cu 2 O is nontoxic and Cu is a common element on earth.…”