Asymmetric Low-Frequency Pulsed Strategy Enables Ultralong CO₂ Reduction Stability and Controllable Product Selectivity

Abstract

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.

Hydrophobic, Ultrastable Cuδ+ for Robust CO2 Electroreduction to C2 Products at Ampere-Current Levels

“…Electroreduction of carbon dioxide (CO 2 RR) to value-added products using renewable energy offers a feasible pathway to realize carbon-neutral energy cycle. , Among various CO 2 RR products, multicarbon (C 2+ ) products, such as C 2 H 4 , C 2 H 5 OH, and CH 3 COOH, have attracted wide attention due to their high energy densities. − Efficient CO 2 -to-C 2+ convention involves multiple proton-coupled electron transfer processes, which accompanied with multiple intermediates on catalytic sites often lead to a low activity and selectivity. Therefore, it is important and challenging to develop effective electrocatalysts for CO 2 RR. , Copper (Cu) materials showed great promise to promote selective electroreduction of CO 2 to C 2+ products with a high conversion efficiency. − Recent studies have demonstrated that the moderate oxidation state of Cu (Cu δ+ ) played a critical role in steering the CO 2 RR pathway toward the high-efficacy C 2+ formation. − However, Cu δ+ active sites are extremely unstable during CO 2 RR, and various strategies, including plasma treatment, heteroatom doping, and organic molecular modification, have been explored to stabilize Cu δ+ . ,,− Recent advances have improved the Faradaic efficiency (FE) toward C 2+ products up to around 80 to 90%. ,− In spite of these efforts, Cu δ+ sites still suffer from the in situ self-reduction during CO 2 RR. This makes it very difficult to maintain a high CO 2 RR activity, especially at high operating current densities …”

Viologen linker as a strong electron-transfer mediator in the covalent organic framework to enhance electrocatalytic CO2reduction

“…1 Among the clean technologies, the electrocatalytic reduction of CO 2 for value-added products using clean electric energy stands out as a particularly attractive and promising solution to reduce carbon emissions. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] To date, many Au-, Ag-, and Cu-based nanostructured materials, metal-organic frameworks, and single-atom catalysts have been developed to apply in the CO 2 electroreduction reaction (CO 2 RR). [16][17][18][19][20][21][22] However, the CO 2 RR generally faces challenges in achieving high selectivity and a high current density due to the intrinsic thermodynamic stability of CO 2 and the competitive hydrogen evolution reaction (HER), hindering its practical application.…”

Pulsed Current Constructs 3DM Cu/ZnO Current Collector Composite Anode for Free-Dendritic Lithium Metal Batteries

“…In addition, some additional applied physical fields have been proven to improve the deposition state of lithium metal [36,37]. Gu et al grew in situ Cu matrix clusters with a tunable oxidation state in Cu 3 (DMPz) 3 by using a simple pulsed method and achieved a high CO2RR performance and ultralong cycling by enhancing their selectivity to C 2 H 4 [38]. Zai et al also prepared Te nanowires with a uniform morphology by controlling the nucleation and growth of crystals via pulsed physical deposition [39].…”