Self-Activation of a Polyoxometalate-Derived Composite Electrocatalyst for the Oxygen Evolution Reaction

• Published in: ACS applied energy materials Vol. 4; no. 11; pp. 12671 - 12676
• Main Authors: Gong, Ruihao, Gao, Dandan, Liu, Rongji, Sorsche, Dieter, Biskupek, Johannes, Kaiser, Ute, Rau, Sven, Streb, Carsten
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.11.2021
• Subjects: oxygen evolution reaction; self-activation; electrocatalysis; TiO2; polyoxometalate; core−shell structure
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.1c02399

The electrocatalytic oxygen evolution reaction (OER) is a key step to access “green hydrogen” by splitting water into O2 and H2. Here, we present a molecule-in-material integration concept based on immobilizing the polyoxometalate (POM) anion ([Co4(H2O)2(PW9O34)2]10–) as a molecular precursor on commercial TiO2 (P25) nanoparticles using the cationic polymer polyethylenimine (PEI) as a linking agent. The resulting composite shows promising electrocatalytic OER performance in 0.1 M aqueous KOH solution over prolonged periods (>10 h), during which a remarkable self-activation is observed, leading to a decreased OER overpotential, increased current density, and high Faradaic efficiency (91 ± 1%). Mechanistic studies shed light on the underlying reasons for this self-activation and show that the formation of a highly active cobalt oxide and/or hydroxide catalyst and an increase in the electrocatalytically active surface area as well as electrical conductivity are the main contributing factors. The reported approach enables the scalable fabrication of POM-derived composite electrocatalysts, while self-activation could be a viable route to the more robust and more active electrocatalysts for challenging energy-conversion reactions.