CO2 electroreduction to fuels on mesoporous carbon-embedded copper nanoparticles

The electrochemical carbon dioxide reduction reaction (CO2RR) process can allow the production of chemicals under ambient conditions on nanostructured copper materials. However, the reaction selectivity is still a main drawback due to strong competition reactions at close electrode potentials. Herein, we introduced a novel three-dimensional electrode composed of mesoporous carbon-embedded copper nanoparticles that are capable of selectively producing formic acid and short-chain hydrocarbons at low overpotentials. The mesoporous electrocatalyst was synthesized from a facile and one-pot green chemistry process using bio-sourced Tannin mimosa (polymeric flavonoids) acting as both reducing agent and carbon precursor. The role of different electrode potentials on the product selectivity (methane and ethylene) was probed by on-line differential electrochemical mass spectrometry (DEMS). During the CO2 electrolysis, chronoamperometry experiments allowed the evaluation of the electrocatalytic performance towards CO2RR with a distinguishable production of formic acid and hydrocarbons. It should be noted that methane was first detected at a potential of −0.52 V, while ethylene showed up at −0.72 V vs. RHE. Moreover, the thin-layer Cu/C ex-tannin porous electrode surface exhibited current densities ranging from 5.9 to 42.1 mA cm−2, which are higher than those previously reported on copper-based electrodes. This suggests that the Cu/C ex-tannin electrocatalyst surface facilitates charge and mass transfers towards accessible active sites through mesostructured carbon paths, boosting the performance for CO2RR. The Cu/C ex-tannin electrode described here may provide a promising lead for the development of effective electrocatalyst structures for scalable electrochemical CO2 reduction electrolyzers.