Carbon‐Doped Amorphous Gallium Oxide Forms a Heterojunction With Water to Improve the Electrocatalytic Oxygen Evolution Reaction

ABSTRACT The weak interactions between powdered catalysts and their supports significantly impact the kinetics of the water electrolysis oxidation reaction. Here, we use plasma‐enhanced atomic layer deposition (PEALD) technology to directly construct amorphous carbon‐doped gallium oxide (ACG) on a glassy carbon (GC) electrode with trimethylgallium (TMGa) and oxygen plasma as oxygen sources. The technique has low saturation pulse periods for the TMGa precursor, a wide temperature range (75°C–300°C), and a steady growth rate of 0.65 Å/cycle. Carbon atom doping induces localized electric fields within the ACG, enhancing the kinetics of the water electrolysis reaction. In addition, electron paramagnetic resonance spectroscopy and theoretical calculations show that ACG forms a catalyst–water–heterojunction structure with water molecules, which promotes the formation of hydroxyl radicals, thus revealing the active origin of GaOOH. Importantly, under the strong oxidizing effect of hydroxyl radicals, carbonate is easily formed, and a weak alkaline layer is formed at the interface of the catalyst, which prevents continuous reconstruction of the GaOOH phase, thus improving the stability of the catalyst in complex media. Meanwhile, it is revealed that ACG follows the lattice oxygen mechanism in the oxygen evolution reaction process. Results indicate that achieving a current of 1000 mA cm ⁻² in an alkaline seawater medium requires only 1.94 V, with stable operation for 200 h showing virtually no attenuation. This study demonstrates the ability to manufacture thin films via PEALD, paving the path toward enhanced electrocatalytic applications.