High-efficiency CO₂ electroreduction on molybdenene: a comparative study using fixed-charge and fixed-potential methods

The electrochemical conversion of renewable energy into fuels and chemicals addresses the energy crisis and environmental pollution. Current CO₂ reduction reaction (CO₂RR) catalysts face challenges like high overpotentials and poor selectivity. Metallenes, with structural advantages and abundant active sites, offer high performance. Notably, molybdenene has excelled in nitrogen reduction reaction electrocatalysis. Herein, we employed three methods, the fixed-charge method (FCM) without and with a solvent effect and the fixed-potential method (FPM), to evaluate molybdenene for the CO₂RR. This material inherently captures and activates CO₂ due to its surplus surface electrons, demonstrating high activity and selectivity, favoring CH₄ production. The optimal pathway, *CO₂ → *OCHO → *OCH₂O → *OCH₂OH → *OCH₂ → *OCH₃ → *O → *OH → *H₂O, exhibits low overpotentials (0.68 V), lower than that of Cu(211). Despite identical overpotentials from the FCM with the solvent effect and the FPM, varying the potential-determining step emphasizes constant potential conditions. These findings underscore the potential of this emerging material as a high-efficiency CO₂RR electrocatalyst, broadening its application prospects and encouraging further theoretical and practical exploration.