Asymmetric Low-Frequency Pulsed Strategy Enables Ultralong CO 2 Reduction Stability and Controllable Product Selectivity.

Copper-based catalysts are widely explored in electrochemical CO 2 reduction (CO 2 RR) because of their ability to convert CO 2 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 Cu 3 (DMPz) 3 catalyst in CO 2 RR. Under traditional potentiostatic conditions, Cu 3 (DMPz) 3 exhibited poor CO 2 RR performance with the Faradaic efficiency (FE) of 34.5% for C 2 H 4 and FE of 5.9% for CH 4 as well as the low stability for less than 1 h. We optimized two distinguished ALPS methods toward CH 4 and C 2 H 4 , correspondingly. The high selectivities of catalytic product CH 4 (FE CH4 = 80.3% and above 76.6% within 24 h) and C 2 H 4 (FE C2H4 = 70.7% and above 66.8% within 24 h) can be obtained, respectively. The ultralong stability for 300 h (FE CH4 > 60%) and 145 h (FE C2H4 > 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 Cu 3 (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 C 2 H 4 selectivity and Cu(I and II) with CH 4 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 CO 2 RR.