Nanoporous Metal–Organic Framework-Based Ellipsoidal Nanoparticles for the Catalytic Electroreduction of CO₂

Electroreduction of carbon dioxide (CO₂) to carbon monoxide (CO) is a promising strategy to reduce the superfluous CO₂ in the atmosphere while simultaneously generating renewable fuel and crucial raw materials for industrial manufacturing. Here, we report a hierarchical nanoporous catalyst with ellipsoidal morphology to achieve efficient CO production from CO₂. By retaining the micropores of the metal–organic framework (MOF) precursor to enhance CO₂ concentration in the gas-diffusion electrode (GDE) and fabricating mesopores during pyrolysis to assist mass transfer, the nanoporous catalyst delivers 200 mA cm^–2 current density at −0.30 V versus the reversible hydrogen electrode (RHE) and near-unity Faradaic efficiency toward CO (FE_CO) of 98.7% under ambient conditions. It also achieved 645 mA cm^–2 CO partial current density (j_CO) at −0.53 V vs RHE with 86% FE_CO, allowing a turnover frequency (TOF) of 159 s^–1 normalized to electrochemically active surface area (ECSA). Electrocatalytic generation of CO and O₂ from CO₂ and water was observed at a cell voltage of only 1.40 V, just slightly above the equilibrium voltage of 1.34 V. Furthermore, the nanoporous catalyst continually delivers CO at 100 mA cm^–2 at −0.6 V vs RHE for 8 h with FE_CO greater than 98%.