Improved Performance of GaN Photoelectrodes from the Facile Fabrication of a Binder-Free Catalyst: Ni(OH)₂ Nanosheets

Abstract

In this work, photoelectrochemical (PEC) reactions were carried out using n-GaN-based photoelectrodes in NaCl electrolytes. During the PEC reactions, the surface of bare n-GaN often gets rough, resulting in more surface defects. As a result, photogenerated carrier recombination with the defects at the n-GaN surface and the photocorrosion of n-GaN photoelectrodes occur simultaneously. Therefore, Ni­(OH)2 nanosheets prepared by a low-cost hydrothermal technique were coated on the n-GaN surface to passivate the surface defects and thereby suppress the photocorrosion of n-GaN photoelectrodes. The coated Ni­(OH)2 nanosheets can enhance band bending between the electrolyte and semiconductor, according to the findings of the Mott–Schottky plot. Furthermore, Ni­(OH)2 nanosheets demonstrate excellent catalytic characteristics in terms of carrier transferability and the ability to suppress surface defects, as evidenced by the evaluations using linear sweep voltammetry and open-circuit potential. According to the findings, Ni­(OH)2 can significantly improve the performance of n-GaN-based electrodes in PEC applications while also protecting them against photocorrosion.

Seed-Assisted Synthesis of Ni(OH)2 Nanosheets on InGaN Films as Photoelectrodes toward Solar-Driven Water Splitting

“…The NiO thickness employed in this study was estimated to be around 3 nm. For the synthesis of Ni­(OH) 2 , NiCl 2 (0.117g) and urea (0.1 g) were dissolved in 40 mL of DI water and stirred for 60 min to form the precursor solution . Subsequently, the NiO/In x Ga 1– x N samples and the bare InGaN samples were immersed in precursor solutions and placed in an autoclave at 180 °C for 120 min.…”

“…For the synthesis of Ni(OH) 2 , NiCl 2 (0.117g) and urea (0.1 g) were dissolved in 40 mL of DI water and stirred for 60 min to form the precursor solution. 19 Subsequently, the NiO/In x Ga 1−x N samples and the bare InGaN samples were immersed in precursor solutions and placed in an autoclave at 180 °C for 120 min. This allowed the growth of Ni(OH) 2 nanosheets on the surface of the In x Ga 1−x N films.…”

“…17,18 Our previous research has demonstrated that Ni(OH) 2 serves as an effective catalyst for reducing the overpotential of the PEC reaction and preventing photocorrosion in photoelectrodes. 19 However, we discovered that when employing the hydrothermal method to prepare Ni(OH)…”

“…Our previous research has demonstrated that Ni­(OH) 2 serves as an effective catalyst for reducing the overpotential of the PEC reaction and preventing photocorrosion in photoelectrodes . However, we discovered that when employing the hydrothermal method to prepare Ni­(OH) 2 nanosheets, the resulting surface coverage on In x Ga 1– x N-based photoelectrodes was limited, leading to inadequate protection against photocorrosion.…”

Effects of FeOOH Nanofilms on Photoelectrochemical Reaction Using Gallium Nitride as Photoelectrodes

“…PEC reactions conducted using n-gallium nitride (GaN) epitaxial films as working electrodes (WEs) have at least one advantage in that GaN is considerably resistant to acidic or alkaline electrolytes compared with Si and GaAs. − In addition, it possesses an appropriate band position to propel the hydrogen evolution reaction and oxygen evolution reaction simultaneously. , Meanwhile, the bandgap of GaN-based semiconductors can be tailored by incorporating indium (In) into Ga 1– x In x N and thereby have a more efficient photoresponse to solar radiation. − Nevertheless, high-quality and sufficiently thick Ga 1– x In x N films are difficult to grow on substrates (e.g., GaN or sapphire). Given the large lattice mismatch between GaN and Ga 1– x In x N, numerous structural defects, such as dislocations, are produced in the films during the epitaxial growth.…”