Catalysis

Oxygen evolution

Phase (matter)

Engineering

Oxide

Transmission electron microscopy

Electrochemistry

Metallurgy

Materials science

Electrowetting

Wetting transition

Inorganic chemistry

Chemical engineering

Physical chemistry

Redox

Contact angle

Nanotechnology

Organic chemistry

Oxygen

Composite material

Cobalt oxide

Chemistry

Electrode

Wetting

Surface energy

Nature Catalysis

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.

Switchable wetting of oxygen-evolving oxide catalysts