High-Valence Oxides for High Performance Oxygen Evolution Electrocatalysis

Valence tuning of transition metal oxides is an effective approach to design high-performance catalysts, particularly for the oxygen evolution reaction (OER) that underpins solar/electric water splitting and metal-air batteries. Recently, high-valence oxides (HVOs) are reported to show superior OER performance, in association with the fundamental dynamics of charge transfer and the evolution of the intermediates. Particularly considered are the adsorbate evolution mechanism (AEM) and the lattice oxygen-mediated mechanism (LOM). High-valence states enhance the OER performance mainly by optimizing the e(g)-orbital filling, promoting the charge transfer between the metal d band and oxygen p band. Moreover, HVOs usually show an elevated O 2p band, which triggers the lattice oxygen as the redox center and enacts the efficient LOM pathway to break the scaling limitation of AEM. In addition, oxygen vacancies, induced by the overall charge-neutrality, also promote the direct oxygen coupling in LOM. However, the synthesis of HVOs suffers from relatively large thermodynamic barrier, which makes their preparation difficult. Hence, the synthesis strategies of the HVOs are discussed to guide further design of the HVO electrocatalysts. Finally, further challenges and perspectives are outlined for potential applications in energy conversion and storage.

Automated summary

Valence tuning of transition metal oxides is an effective approach to design high-performance catalysts for the oxygen evolution reaction (OER). High-valence oxides (HVOs) exhibit superior OER performance due to charge transfer dynamics and the evolution of intermediates. The filling of e(g)-orbitals and the promotion of charge transfer between the metal d band and oxygen p band enhance the OER performance. Additionally, HVOs utilize lattice oxygen as the redox center in the efficient lattice oxygen-mediated mechanism (LOM), overcoming the scaling limitation of the adsorbate evolution mechanism (AEM).