Resolving local reaction environment toward an optimized CO2-to-CO conversion performance

Abstract

The local reaction environment, especially the electrode–electrolyte interface and the relevant hydrodynamic boundary layer in the vicinity of the cathode, plays a vital role in defining the activity and selectivity of the electrochemical CO₂ reduction reaction. Here, we present a differential electrochemical mass spectroscopic (DEMS) approach on the Ag electrode to resolve this information and provide hints for optimized CO₂-to-CO conversion performance. A multi-physics model with computational fluid dynamics and chemical simulation is firstly proposed to demonstrate the flow pattern and the CO₂ distribution within the cathodic DEMS chamber under operational conditions. Using this developed spectroelectrochemical method, we investigate the promotion effects of CO₂ mass transport, cation identity and surface topology on Ag catalyzed CO₂ reduction at a temporal resolution of ∼200 ms. As a proof of concept, these fundamental understandings have been validated in a pilot anion exchange membrane electrolyzer, leading to a CO partial current density above 650 mA cm⁻² at 4.0 V, an operational voltage window wider than 1.0 V and a stable CO generation for 100 hours at 500 mA cm⁻² for CO selectivity above 80%.