The origin of CO2 electroreduction into C1 and C2 species: Mechanistic understanding on the product selectivity of Cu single-crystal faces

CuBi electrocatalysts modulated to grow on derived copper foam for efficient CO2-to-formate conversion

Electrochemical reduction of CO₂ to fuels and chemicals is an effective way to reduce greenhouse gas emissions and alleviate the energy crisis, but the highly active catalysts necessary for this reaction under mild conditions are still rare. In this work, we grew CuBi bimetallic catalysts on derived copper foam substrates by co-electrodeposition, and then investigated the correlation between co-electrodeposition potential and electrochemical performance in CO₂-to-formate conversion. Results showed that the bimetallic catalyst formed at a low potential of - 0.6 V vs. AgCl/Ag electrode achieved the highest formate Faradaic efficiency (FE_formate) of 94.4% and a current density of 38.5 mA/cm² at a low potential of - 0.97 V vs. reversible hydrogen electrode (RHE). Moreover, a continuous-flow membrane electrode assembly reactor also enabled the catalyst to show better performance (a FE_formate of 98.3% at 56.6 mA/cm²) than a traditional H-type reaction cell. This work highlights the vital impact of co-electrodeposition potential on catalyst performance and provides a basis for the modulated growth of bimetallic catalysts on substrates. It also shows the possibility of preparing Bi-based catalysts with no obvious decrease in catalytic activity that have been partially replaced with more economic copper.

Theoretical understanding of the electrochemical reaction barrier: a kinetic study of CO2 reduction reaction on copper electrodes

The electrochemical reduction of CO₂ is a promising route for converting intermittent renewable energy into storable fuels and useful chemical products.

Potential-Dependent CO2 Electroreduction Pathways on Cu(111) Based on an Improved Electrode/Aqueous Interface Model: Determination of the Origin of the Overpotentials

Potential-dependent CO₂ electroreduction pathways on Cu(111) are systematically studied with the aim of applying an improved electrode/aqueous interface model in this paper. The results indicate that our present defined CH₂O and CHOH pathways may be able to parallelly take place at low overpotentials. Notably, the applied potentials will not alter the optimal CO₂ reduction mechanisms. However, the presence of high overpotentials makes CO₂ electroreduction more favorable, thus explaining why high overpotentials at experiments are required during CO₂ electroreduction on Cu. Based on the potential-dependent energetics, the results suggest that COOH and CHO intermediates may be unstable at low overpotentials, in which COOH can easily change back to CO₂ and CHO can easily change back to CO, thus preventing CO₂ electroreduction. However, the high overpotentials will facilitate the formation and further electroreduction of CO and CHO. Thus, we can speculate that CO formation and then further electroreduction into CHO are the possible potential-limiting steps during CO₂ electroreduction, which are regarded as the origin of experimentally observed high overpotentials. The present comprehensive understanding on CO₂ electroreduction pathways can provide theoretical guidelines for efficiently designing Cu-based alloy electrocatalysts operated under the conditions of low overpotentials.

Mechanistic study on Cu-catalyzed CO2 electroreduction into CH4 at simulated low overpotentials based on an improved electrochemical model

An improved CO coverage-dependent electrochemical model with explicit relaxed H2O molecules used in CO2 electroreduction is presented, which is firstly applied to Cu-catalyzed CO2 electroreduction into CH4 production at low overpotentials in this paper. The results show that the present defined CH2O and CHOH pathways via common intermediates CHO and CH2 may be able to occur parallelly at the present simulated low overpotential. The potential-limiting steps may be the formation of CO and its further electroreduction into CHO, which are considered as the origin of the observed experimentally high overpotential. The present study also explains why at electrochemical interfaces, only CH4 is observed experimentally on the Cu surface rather than CH3OH. The present results are found to be in excellent agreement with the available experimental data and partial theoretical analysis, further validating the rationality of the present employed methodology.