Correlative operando microscopy of oxygen evolution electrocatalysts

Article

关键词: QUARTZ-CRYSTAL MICROBALANCE;    WATER OXIDATION;    OXIDES;    ELECTROLYSIS;    STABILITY;    HYDROXIDE;    DYNAMICS;    BEHAVIOR;    STATE;   

DOI  :  10.1038/s41586-021-03454-x

来源: SCIE

【 摘 要 】

Transition metal (oxy)hydroxides are promising electrocatalysts for the oxygen evolution reaction(1-3). The properties of these materials evolve dynamically and heterogeneously(4) with applied voltage through ion insertion redox reactions, converting materials that are inactive under open circuit conditions into active electrocatalysts during operation(5). The catalytic state is thus inherently far from equilibrium, which complicates its direct observation. Here, using a suite of correlative operando scanning probe and X-ray microscopy techniques, we establish a link between the oxygen evolution activity and the local operational chemical, physical and electronic nanoscale structure of single-crystalline beta-Co(OH)(2) platelet particles. At pre-catalytic voltages, the particles swell to form an alpha-CoO(2)H(1.5 center dot)0.5H(2)O-like structure-produced through hydroxide intercalation-in which the oxidation state of cobalt is +2.5. Upon increasing the voltage to drive oxygen evolution, interlayer water and protons de-intercalate to form contracted beta-CoOOH particles that contain Co3+ species. Although these transformations manifest heterogeneously through the bulk of the particles, the electrochemical current is primarily restricted to their edge facets. The observed Tafel behaviour is correlated with the local concentration of Co3+ at these reactive edge sites, demonstrating the link between bulk ion-insertion and surface catalytic activity. Mapping the operational chemical, physical and electronic structure of an oxygen evolution electrocatalyst at the nanoscale links the properties of the material with the observed oxygen evolution activity.

【 授权许可】

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