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 .

This review provides a systematic overview of the integration, surface, and interfacial engineering of 2D/3D and 2D/2D homo/heterojunctions for PV and PEC applications.