The surface wettability of catalysts is typically controlled via surface treatments that promote catalytic performance. Here we report on potential-regulated hydrophobicity/hydrophilicity at cobalt-based oxide interfaces with an alkaline solution. The switchable wetting of single particles, directly related to their activity and stability towards the oxygen evolution reaction, was revealed by electrochemical liquid-phase transmission electron microscopy. Analysis of the movement of the liquid in real time revealed distinctive wettability behaviour associated with specific potential ranges. At low potentials, an overall reduction of the hydrophobicity of the oxides was probed. Upon reversible reconstruction towards the surface oxyhydroxide phase, electrowetting was found to cause a change in the interfacial capacitance. At high potentials, the evolution of molecular oxygen, confirmed by operando electron energy-loss spectroscopy, was accompanied by a globally thinner liquid layer. This work directly links the physical wetting with the chemical oxygen evolution reaction of single particles, providing fundamental insights into solid–liquid interfacial interactions of oxygen-evolving oxides.

催化剂的表面润湿性通常通过促进催化性能的表面处理来控制。在这里，我们报告了钴基氧化物与碱性溶液界面处电位调节的疏水性/亲水性。电化学液相透射电子显微镜揭示了单个颗粒的可切换润湿性，与它们对析氧反应的活性和稳定性直接相关。对液体运动的实时分析揭示了与特定电位范围相关的独特润湿性行为。在低电位下，探索了氧化物疏水性的总体降低。在对表面羟基氧化物相进行可逆重建后，发现电润湿会导致界面电容发生变化。在高电位下，经操作电子能量损失光谱证实，分子氧的演化伴随着全球较薄的液体层。这项工作直接将物理润湿与单个颗粒的化学析氧反应联系起来，为析氧氧化物的固液界面相互作用提供了基本的见解。