Microenvironment Engineering for the Electrocatalytic CO₂ Reduction Reaction

Abstract

Rather than just focusing on the catalyst itself in the electrocatalytic CO 2 reduction reaction (eCO 2 RR), as previously reviewed elsewhere, we herein extend the discussion to the special topic of the microenvironment around the electrocatalytic center and present a comprehensive overview of recent research progress. We categorize the microenvironment based on the components relevant to electrocatalytic active sites, i.e., the catalyst surface, substrate, co-reactants, electrolyte, membrane, and reactor. Supported by most of the reported articles, the relevant factors affecting the catalytic performance of eCO 2 RR are then discussed in detail, and existing challenges and potential solutions are mentioned. Perspectives for the future research on eCO 2 RR, including the integration of different microenvironment factors, the extension to industrial application by coupling with carbon capture and conversion, and separation of products, are also discussed.

Comprehensive understanding and rational regulation of microenvironment for gas‐involving electrochemical reactions

“…51 There are already some reviews recognizing the significance of the microenvironment and summarizing the study of regulating the microenvironment in CO 2 RR. [52][53][54] In this review, we will extend the scope to the common issues of gas-involving electrocatalysis, including CO 2 RR and NRR. Moreover, we precisely classify the multifactors affecting catalytic activity and selectivity in heterogeneous catalytic systems into gas diffusion, proton supply, and electron transfer.…”

“…In the holistic reaction process, several critical factors in this microenvironment are coupled with each other, collectively affecting the behavior of substances (gas, proton, and electron) and the activity and selectivity of electrocatalysis 51 . There are already some reviews recognizing the significance of the microenvironment and summarizing the study of regulating the microenvironment in CO 2 RR 52–54 . In this review, we will extend the scope to the common issues of gas‐involving electrocatalysis, including CO 2 RR and NRR.…”

Three-Phase Interface Construction on Hydrophobic Carbonaceous Catalysts for Highly Active and Selective Photocatalytic CO2 Conversion

“…Recently, the gas (CO 2 )–liquid (aqueous solution)–solid (photocatalyst) three-phase reaction systems have been developed to address the limited CO 2 mass transfer issue in water. ,, The introduction of the gas layer to the liquid–solid boundary was found highly efficient in increasing the local concentration and diffusion rate of CO 2 while diluting the proton content near the catalyst surface, resulting in improved CO 2 RR activity and selectivity. , Iizuka et al reported a method to construct a three-phase interface by continuously bubbling CO 2 throughout the photoreactions, but the system required constant energy consumption to maintain . It was found that the three-phase interface could be regulated by simply tuning the hydrophobic property of the catalyst, substrate, or surface modifier. − ,, For instance, a Pt-loaded photocatalyst modified with a hydrophobic ligand exhibited significant CO 2 RR promotion and HER inhibition due to efficient three-phase contact of CO 2 , water, and catalyst . Recently, fast delivery of CO 2 gas to the catalyst was reported by constructing a hydrophobic–hydrophilic abrupt interface on the hydrophobic substrate .…”

“…22 It was found that the three-phase interface could be regulated by simply tuning the hydrophobic property of the catalyst, substrate, or surface modifier. [16][17][18]23,24 For instance, a Ptloaded photocatalyst modified with a hydrophobic ligand exhibited significant CO 2 RR promotion and HER inhibition due to efficient three-phase contact of CO 2 , water, and catalyst. 17 Recently, fast delivery of CO 2 gas to the catalyst was reported by constructing a hydrophobic−hydrophilic abrupt interface on the hydrophobic substrate.…”

“…16 Although these methods can regulate the three-phase interface, there are still some issues that need to be addressed, such as the passivation of surface active sites, the reduction of catalyst conductivity, and the catalyst shedding issue. 23 Herein, we present a perspective upon constructing a threephase interface on the hydrophobic cocatalyst. The hydrophobic cocatalyst has considerable benefits: (1) the surface properties (e.g., active sites and wettability) and electronic structure of the catalyst can be optimized by adjusting the amount and hydrophobicity of the cocatalysts, 25 (2) the cocatalyst works as an electron sink to facilitate the charge transfer and separation, 26,27 and (3) the convergence of electron and CO 2 on the hydrophobic cocatalyst provides a favorable reaction microenvironment for CO 2 RR.…”