Copper-based catalysts are widely explored in electrochemical CO₂reduction (CO₂RR) because of their ability to convert CO₂ into high-value-added multi-carbon 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. In 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 towards CH₄ and C₂H₄, correspondingly. The high selectivities of catalytic product CH₄(FE_CH4 = 80.3% and above 76.6% within 24 h) and C₂H₄ (FE_C2H4 = 70.7% and above 66.8% within 24 h) can be obtained, respectively. The ultra-long stability for 300 hours (FE_CH4 > 60%) and 145 hours (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 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.

A simple and efficient method of asymmetric low-frequency pulsed strategy (ALPS) was proposed to significantly enhance the stability and the selectivity of Cu-based catalyst in CO₂RR.

Zhi-Yuan Gu

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