The iridium oxide (IrO ₂ ) catalyst for the oxygen evolution reaction used industrially (in proton exchange membrane water electrolyzers) is scarce and costly. Although ruthenium oxide (RuO ₂ ) is a promising alternative, its poor stability has hindered practical application. We used well-defined extended surface models to identify that RuO ₂ undergoes structure-dependent corrosion that causes Ru dissolution. Tantalum (Ta) doping effectively stabilized RuO ₂ against such corrosion and enhanced the intrinsic activity of RuO ₂ . In an industrial demonstration, Ta-RuO ₂ electrocatalyst exhibited stability near that of IrO ₂ and had a performance decay rate of ~14 microvolts per hour in a 2800-hour test. At current densities of 1 ampere per square centimeter, it had an overpotential 330 millivolts less than that of IrO ₂ .

Understanding charge transfer dynamics and carrier separation pathway is challenging due to the lack of appropriate characterization strategies. In this work, a crystalline triazine/heptazine carbon nitride homojunction is selected as a model system to demonstrate the interfacial electron-transfer mechanism. Surface bimetallic cocatalysts are used as sensitive probes during in situ photoemission for tracing the S-scheme transfer of interfacial photogenerated electrons from triazine phase to the heptazine phase. Variation of the sample surface potential under light on/off confirms dynamic S-scheme charge transfer. Further theoretical calculations demonstrate an interesting reversal of interfacial electron-transfer path under light/dark conditions, which also supports the experimental evidence of S-scheme transport. Benefiting from the unique merit of S-scheme electron transfer, homojunction shows significantly enhanced activity for CO₂ photoreduction. Our work thus provides a strategy to probe dynamic electron transfer mechanisms and to design delicate material structures towards efficient CO₂ photoreduction.