Spectroelectrochemical Investigation of the Local Alkaline Environment on the Surface-Nanostructured Au for the Conversion of CO2 to CO

The electrocatalytic conversion of carbon dioxide (CO2) into fuels could potentially achieve a sustainable carbon-basedeconomy. The engineering of nanostructured metal electrodes can enhancetheir activity and selectivity by controlling their local chemicalenvironment; however, direct observation is challenging. In this study,we investigate the molecular-level reaction mechanism of a nanoporous-structuredAu electrode for the conversion of CO2 to carbon monoxide(CO) using surface-enhanced infrared absorption spectroscopy (SEIRAS).We designed a well-structured nanoporous Au layer (with a depth distributionof 56.3 nm) on a Si prism using a high-temperature non-aqueous anodizationprocess and characterized the nanoporous Au electrode using atomicforce microscopy (AFM) and X-ray absorption spectroscopy (XAS). Thein situ SEIRAS results demonstrated that the nanoporous Au electrodehas a dominant active site, promoting the linear CO intermediate andsuppressing the bridging CO intermediate when compared with the non-structuredAu electrode. We also revealed a high local pH at a reaction potentialof -0.9 V and the slow diffusion kinetics of local CO3 (2-) at an open-circuit potential. These findingsprovide deeper insights into the electrochemical kinetics and correspondingmechanisms occurring in the electric double layers and highlight thepotential for the design of efficient electrocatalysts for CO2 reduction.

Automated summary

In this study, the molecular-level reaction mechanism of nanoporous gold electrodes for the conversion of carbon dioxide to carbon monoxide was investigated using surface-enhanced infrared absorption spectroscopy (SEIRAS). It was found that the nanoporous gold electrodes promoted the formation of linear CO intermediate and suppressed the formation of bridging CO intermediate. The study also revealed a high local pH and slow diffusion kinetics of local CO3 (2-) at specific reaction potentials. These findings provide insights into the electrochemical kinetics and mechanisms occurring in the electric double layers, highlighting the potential for designing efficient electrocatalysts for CO2 reduction.