Photoelectrochemistry of Self‐Limiting Electrodeposition of Ni Film onto GaAs

Abstract

Gallium arsenide (GaAs) provides a suitable bandgap (1.43 eV) for solar spectrum absorption and allows a larger photovoltage compared to silicon, suggesting great potential as a photoanode toward water splitting. Photocorrosion under water oxidation condition, however, leads to decomposition or the formation of an insulating oxide layer, which limits the photoelectrochemical performance and stability of GaAs. In this work, a self‐limiting electrodeposition method of Ni on GaAs is reported to either generate ultra‐thin continuous film or nanoislands with high particle density by controlling deposition time. The self‐limiting growth mechanism is validated by potential transients, X‐ray photoelectron spectroscopy composition and depth profile measurements. This deposition method exhibits a rapid nucleation, forms an initial metallic layer followed by a hydroxide/oxyhydroxide nanofilm on the GaAs surface and is independent of layer thickness versus deposition time when coalescence is reached. A photocurrent up to 8.9 mA cm−2 with a photovoltage of 0.11 V is obtained for continuous ultrathin films, while a photocurrent density of 9.2 mA cm−2 with a photovoltage of 0.50 V is reached for the discontinuous nanoislands layers in an aqueous solution containing the reversible redox couple K3Fe(CN)6/K4Fe(CN)6.

Voltage-Controlled ON–OFF-Switching of Magnetoresistance in FeOx/Fe/Au Aerogel Networks

“…Self-terminating electrodeposition has proved to be a route to fabricate ultrathin, high-quality transition metal films with controllable thickness . Self-termination occurs at very negative deposition potentials, where concurrent water reduction yields a strong increase of pH in front of the electrode. ,− In case of iron electrodeposition, this causes the formation of an iron hydroxide layer, which quenches initial iron electrodeposition and enhances the stability of the deposits in the electrolyte. , …”

Investigation of in situ sulfide/nitride/phosphide treatments of hematite photoanodes for improved solar water oxidation

“…[15][16][17] How to achieve surface engineering, with controllable heterogeneous junctions and effective action scope and without introducing additional defects, has become the research focus and a difficult challenge. 18,19 It may be addressed by in situ surface functional sulfide/nitride/phosphide treatments along with the formation of metal chalcogenides and coordination complexes, which effectively promote surface photogenerated carrier transport without introducing additional defects. 20,21 For sulfide treatments, transition metal chalcogenides (S and Se) have received a lot of attention as promising OER catalysts due to their unique electronic structures.…”

Reliable bi-functional nickel-phosphate /TiO2 integration enables stable n-GaAs photoanode for water oxidation under alkaline condition

“…Recently, a GaAs photoanode was stabilized using surface protection oxides with the precious metal electrocatalysts, eventually promoting the reaction kinetics [19][20][21] . Conducting polymer films such as polypyrrole, polystyrene, and polythiophene have been coated on GaAs, but the stability of these systems is limited by peeling of the film, and the electrodes reveal active photocorrosion 22,23 .…”