Highly selective and effective formate and acetate production from CO2 electroreduction on cathodized metal–organic framework nanosheets.

Electrochemical reduction of CO2 to obtain high-value-added feedstocks is a promising strategy to alleviate the energy crisis. Cu-based catalysts generate multi-carbon products with high activity in the CO2 reduction reaction (CO2RR), although great challenges remain in the selectivity and stability of Cu-based catalysts. Here, highly active Cu/Cu2O nanoclusters were produced via in situ electrochemical reconstruction using Cu–N coordinated MOFs as precursors for the highly selective C2H4 synthesis, showing a Faradaic efficiency of 70.2 ± 1.7% toward C2H4 with a partial current density of 12.38 mA·cm–2 at −1.03 V vs RHE in the CO2RR. In situ infrared spectroscopy with the observation of *CO*CO and *CO*COH intermediates confirmed the C2H4 formation pathway, while in situ Raman spectroscopy, ex situ XPS, and HRTEM evidenced that the coexisting Cu2O and Cu nanoclusters were the active sites. The in situ reconstruction method could be used to synthesize catalysts with high activity and selectivity for CO2 electroreduction.

Copper-based catalysts are widely explored in electrochemical CO2 reduction (CO2RR) because of their ability to convert CO2 into high-value-added multicarbon products. However, the poor stability and low selectivity limit the practical applications of these catalysts. Here, we proposed a simple and efficient asymmetric low-frequency pulsed strategy (ALPS) to significantly enhance the stability and the selectivity of the Cu-dimethylpyrazole complex Cu3(DMPz)3 catalyst in CO2RR. Under traditional potentiostatic conditions, Cu3(DMPz)3 exhibited poor CO2RR performance with the Faradaic efficiency (FE) of 34.5% for C2H4 and FE of 5.9% for CH4 as well as the low stability for less than 1 h. We optimized two distinguished ALPS methods toward CH4 and C2H4, correspondingly. The high selectivities of catalytic product CH4 (FECH4 = 80.3% and above 76.6% within 24 h) and C2H4 (FEC2H4 = 70.7% and above 66.8% within 24 h) can be obtained, respectively. The ultralong stability for 300 h (FECH4 > 60%) and 145 h (FEC2H4 > 50%) was also recorded with the ALPS method. Microscopy (HRTEM, SAED, and HAADF) measurements revealed that the ALPS method in situ generated and stabilized extremely dispersive and active Cu-based clusters (∼2.7 nm) from Cu3(DMPz)3. Meanwhile, ex situ spectroscopies (XPS, AES, and XANES) and in situ XANES indicated that this ALPS method modulated the Cu oxidation states, such as Cu(0 and I) with C2H4 selectivity and Cu(I and II) with CH4 selectivity. The mechanism under the ALPS methods was explored by in situ ATR-FTIR, in situ Raman, and DFT computation. The ALPS methods provide a new opportunity to boost the selectivity and stability of CO2RR.