Observation on Microenvironment Changes of Dynamic Catalysts in Acidic CO₂ Reduction

Abstract

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.

Recent advances in dynamic reconstruction of electrocatalysts for carbon dioxide reduction

“…A good example is the dynamic evolution of a Bi-based catalyst under acidic CO 2 RR conditions. 122 In a long-term stability test of acidic CO 2 RR, the pristine BiOCl catalyst was degraded by reduction and dechlorination reactions, reacted with CO 2 and OH − to form the Bi 2 O 2 CO 3 transient phase, and then completely reduced to the Bi phase. Because the competitive adsorption between the K + and proton was affected by the surface charge property of the dynamic catalyst, the local pH changed from neutral to acid during the dynamic evolution of BiOCl to Bi, resulting in the FE of HCOOH dropping from 91 to 34% within 10 h. To improve the stability of acidic CO 2 RR, a pulsed electrolysis technique was developed to regenerate the original phase of the BiOCl catalyst in a chloride-containing electrolyte.…”

Solid Electrolytes for Low-Temperature Carbon Dioxide Valorization: A Review

“…Efforts are critically needed to gain a deeper understanding of the precise reaction mechanisms involved in CO 2 capture and CO 2 RR, by conducting a comprehensive approach including spectrochemical analysis, theoretical calculations, and isotopic labeling. − For example, utilizing multimodal operando techniques in combination with theoretical calculations can provide insights into the dynamic changes in catalyst structure during CO 2 RR . These molecular-scale understandings are essential for customizing the microenvironment of the dynamic solid–liquid interface to favor desired reaction pathways. , …”

Reaction Environment Regulation for Electrocatalytic CO2 Reduction in Acids

“…[124] The dominant CO 2 RR should be performed under high interface pH conditions; however, the local pH change during electrolysis is deemed a crucial determinant that induces the dynamic evolution of electrocatalysts and gradual FE decay. [63] This suggests that quantitative measurement of the local pH is important for system optimization. The local pH on micro-and nanometer length scales can be experimentally measured by two methods: an in situ optical technique (SERS, fluorescence microscopy, and UVvis spectroscopy) and a pH probe (rotating ring-disk electrode (RRDE), non-Faradaic reaction, etc.).…”

“…Regeneration strategies involving manipulation of operating conditions, i.e., pulsed electrolysis in galvanostatic or potentiostatic mode, also have great potential for periodically restoring oxidized or reduced active sites on Cu and BiOCl electrocatalysts with enhanced product selectivity. [63,77] However, the degradation processes are very complex and might be executed by several factors simultaneously. Understanding the degradation mechanism and the structure-activity relationship is the key to designing robust electrocatalysts.…”