Structural Investigation of the Cu/W/Co-based Mixed Metal Oxide Electrocatalyst using X-ray absorption Spectroscopy.

Mixed metal oxide is an attractive electrocatalyst class for efficient water splitting, yet the identification of real active sites and understanding of synergistic effects are still insufficient. Here, we applied in situ synchrotron-based X-ray absorption spectro-electrochemistry (XAS-EC) to explore the bifunctional mixed Co-Cu-W oxide interface under electrocatalytic conditions. Our investigation, including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), elucidated the dynamic structural transformations of Co, Cu, and W during the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Ex situ XAS measurements indicate the local chemistry of the focused metal centers. The subsequent XAS-EC XANES and EXAFS measurements shed light on the chemical and structural evolution of the Co-Cu-W oxide, in which Co and Cu actively participate in OER and HER while W plays a crucial role as structure stabilizer. This approach provides a valuable means of revealing the complex catalytic mechanism of significantly emerging mixed metal oxide electrocatalysts for advanced water splitting.