Self-Activation of a Polyoxometalate-Derived Composite Electrocatalyst for the Oxygen Evolution Reaction
Ruihao Gong, Dandan Gao, Rongji Liu, Dieter Sorsche, Johannes Biskupek, Ute Kaiser, Sven Rau, Carsten Streb
Abstract
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.