Robust Electrocatalytic CO<sub>2</sub> Reduction in Acid Enabled by “Molecularly Charged” Cobalt Phthalocyanine: A Profound Understanding from Electric Double Layer
Zhenyang Jiao, Daqi Song, Le Wei, Mutian Ma, Wei Hua, Zhangyi Zheng, Min Wang, Yanhui Su, Xiaoxing Ke, Fenglei Lyu, Zhao Deng, Jun Zhong, Yang Peng
Abstract
Electrocatalytic CO 2 reduction (eCO 2 R) in acid holds promise in renewable electricity-powered CO 2 utilization with high efficiency, but the hydrogen evolution reaction (HER) often prevails and results in a low eCO 2 R selectivity. Here, using cobalt phthalocyanine/Ketjen black (CoPc/KB) as the model catalysts, we systematically study the effect of active site density, operational current density, and hydrated cations on the acidic eCO 2 R selectivity and decipher it through the componential dynamics of electric double layer (EDL). The optimal CoPc-4/KB demonstrates a near-unity CO Faradaic efficiency from 50 to 400 mA cm –2 and superb operational stability (>120 h) at 100 mA cm –2 . Aided by in situ Raman and infrared spectroscopies, we reveal that the proper cations establish an electrostatic shield for mitigating bulk H + penetration and mediate the interfacial water structure for suppressing HER. This study should elicit further profound thinking on robust eCO 2 R system design from the perspective of multiphasic and dynamic EDL.