<i>In Situ</i> ATR Infrared Study of Cobalt-Borate Water Oxidation Catalysts

Understanding the process of water oxidation, especially intermediate species, represents an important step toward gaining a mechanistic understanding of new emerging catalysts. The aim of this study is exploring the process of water oxidation and electrolyte orientation under external potential when using an emerging water oxidation catalyst, CoB i , in sodium borate (NaBi) buffer using in situ attenuated–total-reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectroscopy. CoB i is generated via electrodeposition from aqueous solutions containing borate and Co 2+ . IR spectra were obtained for CoB i films under applied potentials supporting water oxidation catalysis. The spectra of water and CoB i on ZnSe/Cr/Au electrode surfaces change in intensity and their slope depends on the potential, which is rarely reported. The appearance of new bands at certain potentials is interpreted in terms of the potential-dependent re-alignment of water and borate molecules both from the film and electrolyte. A superoxide surface intermediate at 1027 cm -1 was observed in both thin and thick films. It is proposed to be Co (III)OO*H bridging and relates to a fast water oxidation process. The chemical structure of the intermediate species is proposed finally.