Sub-2 nm mixed metal oxide for electrochemical reduction of carbon dioxide to carbon monoxide

Abstract

Mixed metal oxide (MMO) represents a critical class of materials that can allow for obtaining a dynamic interface between its components: reduced metal and its metal oxide counterpart during an electrocatalytic reaction. Here, a synthetic method utilizing a MOF-derived micro/mesoporous carbon as a template to prepare sub-2 nm MMO catalysts for CO2 electroreduction is reported. Starting from the zeolite imidazolate framework (ZIF-8), the pyrolyzed derivatives were used to synthesize sub-2 nm Pd-Ni MMO with different compositions. The Ni-rich (Pd20-Ni80/ZC) catalyst exhibits unexpectedly superior performance for CO production with an improved Faradaic efficiency (FE) of 95.3% at the current density of 200 mA cm−2 at −0.56 V vs. reversible hydrogen electrode (RHE) compared to other Pd-Ni compositions. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of Ni2+ and Pd2+ in all compositions, demonstrating the presence of MMO. Density functional theory (DFT) calculation reveals that the lower CO binding energy on the surface of the Pd20-Ni80 cluster eases CO desorption, thus increasing its production. This work provides a general synthetic strategy for MMO electrocatalysts and can pave a new way for screening multimetallic catalysts with a dynamic electrochemical interface.