Benchmarking the Intrinsic Activity of Transition Metal Oxides for the Oxygen Evolution Reaction with Advanced Nanoelectrodes

Abstract The intrinsic activity assessment of transition metal oxides (TMOs) as key electrocatalysts for the oxygen evolution reaction (OER) has not been standardized due to uncertainties regarding their structure and composition, difficulties in accurately measuring their electrochemically active surface area (ECSA), and deficiencies in mass‐transfer (MT) rates in conventional measurements. To address these issues, we utilized an electrodeposition‐thermal annealing method to precisely synthesize single‐particle TMOs with well‐defined structure and composition. Concurrently, we engineered low roughness, spherical surfaces for individual particles, enabling precise measurement of their ECSA. Furthermore, by constructing a conductor‐core semiconductor‐shell structure, we evaluated the inherent OER activity of perovskite‐type semiconductor materials, broadening the scope beyond just conductive TMOs. Finally, using single‐particle nanoelectrode technique, we systematically measured individual TMO particles of various sizes for OER, overcoming MT limitations seen in conventional approaches. These improvements have led us to propose a precise and reliable approach to evaluating the intrinsic activity of TMOs, not only validating the accuracy of theoretical calculations but also revealing a strong correlation of OER activity on the melting point of TMOs. This discovery holds significant importance for future high‐throughput material research and applications, offering valuable insights in electrocatalysis.