Operando X-ray spectroscopy visualizing the chameleon-like structural reconstruction on an oxygen evolution electrocatalyst†
The ambiguous mechanism of electrocatalysts for the oxygen evolution reaction (OER) greatly hinders their industrial applications toward renewable and clean energy conversion. Here, we elaborately prepared a cobalt sulfide catalyst to perform a comprehensive study of the OER performance under neutral/alkaline conditions. The combination of synchrotron-based operando X-ray spectroscopic investigations and electron microscopy observations captured a chameleon-like structural self-optimization on the cobalt sulfide oxygen evolution electrocatalyst in both neutral and alkaline electrolytes. Driven by the actual working conditions (pH gradient, electrical potential, etc.), distinct catalytic sites could be activated dramatically. In particular, the CoOOH supported on a single-walled carbon nanotube (CoOOH-SWCNT) with residual S species was identified as the true catalyst under alkaline conditions rather than the entirely transformed CoOOH-SWCNT, while the oxygenated CoS-SWCNT (O-CoS-SWCNT) was formed as the true catalyst under neutral conditions. Undoubtedly, such a mechanism of opening different locks with different keys and its microstructural advantages together guarantee the high catalytic activity in different electrolytes. This work provides a promising catalyst as well as sheds light on the very essence of the structural self-optimization process of catalysts. It makes a significant contribution to the advancement of OER relevant studies in the future while providing new ideas for the fields of chemistry and catalysis.