Ultrastable atomic copper nanosheets for selective electrochemical reduction of carbon dioxide

The electrochemical conversion of CO₂ and H₂O into syngas using renewably generated electricity is an attractive approach to simultaneously achieve chemical fixation of CO₂ and storage of renewable energy. Developing cost-effective catalysts for selective electroreduction of CO₂ into CO is essential to the practical applications of the approach. We report a simple synthetic strategy for the preparation of ultrathin Cu/Ni(OH)₂ nanosheets as an excellent cost-effective catalyst for the electrochemical conversion of CO₂ and H₂O into tunable syngas under low overpotentials. These hybrid nanosheets with Cu(0)-enriched surface behave like noble metal nanocatalysts in both air stability and catalysis. Uniquely, Cu(0) within the nanosheets is stable against air oxidation for months because of the presence of formate on their surface. With the presence of atomically thick ultrastable Cu nanosheets, the hybrid Cu/Ni(OH)₂ nanosheets display both excellent activity and selectivity in the electroreduction of CO₂ to CO. At a low overpotential of 0.39 V, the nanosheets provide a current density of 4.3 mA/cm² with a CO faradaic efficiency of 92%. No decay in the current is observed for more than 22 hours. The catalysts developed in this work are promising for building low-cost CO₂ electrolyzers to produce CO.