Plasma-Induced Vacancy Defects in Oxygen Evolution Cocatalysts on Ta₃N₅ Photoanodes Promoting Solar Water Splitting

Surface recombination is a critical issue for tantalum nitride (Ta 3 N 5 )-based photoanodes in solar water splitting application. The efficient cocatalysts (Ni-, Fe-, and Co-based) have been developed to promote the electron–hole separation and transportation but still have limited success in some cases. Herein, we studied the Ar plasma-induced etching strategy on the pristine Ta 3 N 5 nanotubes and Co(OH) x -decorated Ta 3 N 5 nanotubes. The Ar plasma can not only destroy the recombination center (TaO) in the interface between the Ta 3 N 5 and electrolyte, resulting in a fast charge transfer, but also most importantly generate more oxygen vacancies with a high ratio of Co 2+ /Co 3+ and produce a higher surface area in the Co(OH) x cocatalyst. The more active sites on Ta 3 N 5 and abundant oxygen vacancies on cocatalyst synergetically contribute to the enhanced solar water splitting activity, which give rise to a fast water oxidation reaction in the interface. The resulting photoanode shows double the performance improvement under AM 1.5G sunlight conditions. Interface-defect engineering is proven to be an efficient and facile strategy to enhance the solar water oxidation activity of Ta 3 N 5, which highlights the advantages of the plasma-etching strategy for establishing the highly active cocatalysts on photoanodes in terms of the conversion of solar energy into chemical energy.