Revealing the Surface Species Evolution on Low‐loading Platinum in an Electrochemical Redox Reaction by Operando Ambient‐Pressure X‐ray Photoelectron Spectroscopy

The stability and activity of Platinum catalysts under the redox process are the key parameters affecting catalytic performance. Here, we investigated the surface species evolution of low‐loading Pt catalyst deposited on a Nafion membrane through e‐beam deposition during redox reactions by using in situ X‐ray photoelectron spectroscopy (XPS) combined with a static electrochemical cell. Operando ambient‐pressure XPS measurement revealed the oxide species (Ptδ+, Pt2+, and Pt4+) evolution over different potentials in the water layer constructed by an acid solution. The amount of Pt2+ increased with an increment of the anodic potential, whereas Pt4+ suddenly formed when the threshold voltage of the oxygen evolution reaction was crossed. Hysteresis of Pt2+ was revealed as Pt4+ was completely reduced when returning to the open circuit potential. Incorporating depth‐profiling studies enabled us to uncover the mechanism of oxide species evolution between the surface and subsurface of the Pt catalyst during a redox reaction. The surface species evolution on membrane electrode with low‐loading Platinum catalyst is investigated by operando ambient‐pressure X‐ray photoelectron spectroscopy. The results provide a better understanding of the interaction between the conductive metallic Pt catalyst and hydrophilic oxide overlayer for oxygen evolution reaction.