Spectro-Electrochemical Insights into Electrocatalytic CO<sub>2</sub> Reduction in Acidic Media through Model Catalyst Design
Jian Cheng, Zhangyi Zheng, Xinyu Zhang, Min Wang, Lingyu Wang, Yang Wang, Xiang Chen, Zhao Deng, Yang Peng
Abstract
Electrocatalytic CO 2 reduction (eCO 2 R) under acidic conditions is the game changer of resourceful CO 2 utilization owing to the alleviated carbon loss but faces severe competition from the hydrogen evolution reaction (HER) that greatly curtails the electric current efficiency. Leveraging the eCO 2 R side of the teeterboard calls for a fundamental understanding of the triphasic electrode process involving a complex arrangement of electric double layers (EDLs). Herein, a series of model catalysts with tailored cavernous parameters are fabricated to geometrically and spectroscopically decipher the competing HER and eCO 2 R processes that engage different proton sources. A comprehensive set of in situ/ operando spectro-electrochemical tools, including differential electrochemical mass spectrometry, vibrational spectra (Raman and Infrared), and rotating disk electrode, are combined to interrogate the geometrically modulated HER and eCO 2 R kinetics with exceptional temporal and spectral resolutions. We uncover that an overcrowded EDL zone comprising capacitively stored K + cations in closely packed nanocages disfavors eCO 2 R at high current densities via limited reaction volume, restrained CO 2 supply, and escalated water dissociation. We further show that, by meticulously crafting the mesoporous cavity structure and suitably expanding the hierarchical EDL zone, great acidic eCO 2 R performance of near-unity CO Faradaic efficiency can be achieved across a wide current range over a prolonged operation. This work offers profound insights into the spatial regulation of mass transport, local chemical environment, and EDL arrangement via tailored catalyst geometry toward high-efficiency eCO 2 R.