Electrochemical carbon monoxide reduction is a promising strategy for the production of value-added multicarbon compounds, albeit yielding diverse products with low selectivities and Faradaic efficiencies. Here, copper single atoms anchored to Ti3C2Tx MXene nanosheets are firstly demonstrated as effective and robust catalysts for electrochemical carbon monoxide reduction, achieving an ultrahigh selectivity of 98% for the formation of multicarbon products. Particularly, it exhibits a high Faradaic efficiency of 71% towards ethylene at −0.7 V versus the reversible hydrogen electrode, superior to the previously reported copper-based catalysts. Besides, it shows a stable activity during the 68-h electrolysis. Theoretical simulations reveal that atomically dispersed Cu–O3 sites favor the C–C coupling of carbon monoxide molecules to generate the key *CO-CHO species, and then induce the decreased free energy barrier of the potential-determining step, thus accounting for the high activity and selectivity of copper single atoms for carbon monoxide reduction.

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Efficient electrocatalytic activity for CO2 reduction based on CuS nanosheet arrays is first presented. The resultant electrode exhibits high catalytic activity and durability for CO2 electroreduction.

Energy crisis and environmental pollution trigger the development of efficient and robust electrochemical energy conversion and storage technologies. [1-3] The electrocatalytic reactions, such as hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR), undoubtedly play key roles in developing renewable energy conversion devices, Development of cost-effective, active trifunctional catalysts for acidic oxygen reduction (ORR) as well as hydrogen and oxygen evolution reactions (HER and OER, respectively) is highly desirable, albeit challenging. Herein, singleatomic Ru sites anchored onto Ti 3 C 2 T x MXene nanosheets are first reported to serve as trifunctional electrocatalysts for simultaneously catalyzing acidic HER, OER, and ORR. A half-wave potential of 0.80 V for ORR and small overpotentials of 290 and 70 mV for OER and HER, respectively, at 10 mA cm −2 are achieved. Hence, a low cell voltage of 1.56 V is required for the acidic overall water splitting. The maximum power density of an H 2-O 2 fuel cell using the as-prepared catalyst can reach as high as 941 mW cm −2. Theoretical calculations reveal that isolated Ru-O 2 sites can effectively optimize the adsorption of reactants/intermediates and lower the energy barriers for the potentialdetermining steps, thereby accelerating the HER, ORR, and OER kinetics.

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The ambient electrocatalytic N2 reduction reaction (NRR) is a promising alternative to the Haber–Bosch process for producing NH3. However, a guideless search for single-atom-based and other electrocatalysts cannot promote the NH3 yield rates by NRR efficiently. Herein, our first-principles calculations reveal that the successive emergence of vertical end-on *N2 and oblique end-on *NNH admolecules on single metal sites is key to high-performance NRR. By targeting the admolecules, single Ag sites with the Ag–N4 coordination are found and synthesized massively. They exhibit a record-high NH3 yield rate (270.9 μg h–1 mgcat. –1 or 69.4 mg h–1 mgAg –1) and a desirable Faradaic efficiency (21.9%) in HCl aqueous solution under ambient conditions. The generation rate of NH3 is stable during 20 consecutive reaction cycles, and the reduction current density is almost constant for 60 h. This work provides an effective targeting-design principle to purposefully synthesize active and durable single-atom-based NRR electrocatalysts.