Observation on Microenvironment Changes of Dynamic Catalysts in Acidic CO 2 Reduction.

Electrochemical CO 2 reduction reaction (CO 2 RR) in acid can solve alkalinity issues while highly corrosive and reductive acidic electrolytes usually cause catalyst degradation. Inhibiting catalyst degradation is crucial for the stability of acidic CO 2 RR. Here, we reveal the microenvironment changes of dynamic Bi-based catalysts and develop a pulse chronoamperometry (CA) strategy to improve the stability of acidic CO 2 RR. In situ fluorescence mappings show that the local pH changes from neutral to acid, and the in situ Raman spectra reveal the dynamic evolution of interfacial water structures in the microenvironment. We propose that the surface charge properties of dynamic catalysts affect the competitive adsorption of K + and protons, thereby causing the differences in local pH and CO 2 RR intermediate adsorption. We also develop a pulse CA strategy to reactivate catalysts, and the stability of acidic CO 2 RR is improved by 2 orders of magnitude for 100 h operation, which is higher than most reports on the stability of acidic CO 2 RR. This work gives insights on how microenvironment changes affecting the stability of acidic CO 2 RR, and provides guidance for designing stable catalysts in acidic electrolytes.