摘要
The challenge of converting carbon dioxide (CO 2 ) electroreduction into high value-added products is to obtain highly selective electrocatalysts. Research has shown that cuprous oxide (Cu 2 O) effectively facilitates the activation of CO 2 and suppress the competing hydrogen evolution reaction. However, during the process of electrochemical reduction, the valence state of Cu 2 O is prone to transformation. Herein, a series of Cu 2 O–CeO 2 -X catalysts (X represents different amounts of CeO 2 added) by applying Cu 2 O onto Cerium oxide (CeO 2 ) nanorods were synthesized via the impregnation method and used as electrocatalysts. We found that the Faradaic efficiency of methane (FE-CH 4 ) for Cu 2 O–CeO 2 -2 reached 65.1 % at −1.6 V vs. RHE, exceeding many catalysts previously reported. From the Cu LMM Auger spectra, it was found that the valence state of Cu species in Cu 2 O–CeO 2 -2 is mainly Cu 0 (accounting for 93.39 %), while in Cu 2 O–CeO 2 -3, the proportion of Cu 0 is 56.34 %. This indicates that CeO 2 has a regulatory effect on the valence state of Cu species. Additionally, we observed the valence state of Cu in Cu 2 O–CeO 2 -2 after the CO 2 reduction reaction and found that the proportion of Cu 0 changed little (94.97 %), which proves that CeO 2 plays a role in stabilizing the valence state of Cu. Research has demonstrated that Cu 0 can adsorb the ∗CO intermediate on its surface, followed by a hydrogenation reaction to generate CH 4 (∗CO + H + + e − → ∗CHO). Copper-based catalysts in which Cu 0 dominates among the Cu species are conducive to the conversion of CO 2 into CH 4 . In situ ATR-SEIRAS spectra confirmed the presence of key intermediates such as ∗CHO and explored the formation pathway of CH 4 (CO 2 → ∗COOH → ∗CO → ∗CHO → ∗OCH 2 → CH 4 ). This study provides a new way to design efficient copper oxide-based catalysts for CO 2 electroreduction by adjusting and stabilizing the ratio of copper valence state reasonably.
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