Zhijian Chen,Zhenghui Ma,Wenlin Yang,Guoli Fan,Baoming Ren,Feng Li
Due to the high energy barrier of C-C coupling and the intense competition from by-products, achieving superior ethylene selectivity in electrochemical CO2 reduction reaction (eCO2RR) remains challenging. Herein, we reported a distinctive Cu-based electrocatalyst fabricated from a three-dimensional (3D) tentacle-like Cu2(OH)2CO3 precursor. After electrochemical activation, abundant surface structural hydroxyls chemically bonded to Cu+ species (Cu+-OH structures) formed on the resulting Cu-based electrocatalyst. Such structural hydroxyl-rich Cu-based catalyst exhibited excellent eCO2RR performance, with a Faradaic efficiency (FE) of 43.7% for ethylene (partial current density up to 130.6 mA·cm-2) and a FE of ~70% for C2+ products at -1.5 V vs RHE in a flow cell, far exceeding those over the hydroxyl-deficient Cu-based one. By combining operando spectroscopic analysis with density functional theory calculations, it was unveiled that inherent surface Cu+-OH structures over Cu-based electrocatalysts could result in the electron loss of neighboring active Cu0 sites, which was favorable for the creation of crucial *COH and *OCCOH intermediates and thus the formation of ethylene product. Consequently, dual reaction pathways for the eCO2RR based on both key *COH and *CHO intermediates coexisting on the Cu-based electrocatalyst with abundant Cu+-OH structures powerfully boosted electrochemical CO2 reduction to produce ethylene. This work presents an innovative strategy for the construction of Cu-based electrocatalyst rich in structural hydroxyls and highlights the crucial role of inherent Cu+-OH structures in switching the formation of intermediates to boost ethylene production in the eCO2RR.
Transition metal hydroxyl oxides have been used widely as ozone catalysts for water purification. However, the fabrication methods selected and the pollutants treated vary, making it difficult to compare their performance. In this study, ZnOOH, FeOOH, CoOOH, and MnOOH were synthesized by the same method to remove multiple structurally similar targets. Results showed that the ZnOOH performed the best, removing over 90 % of all targets within 40 min, and presenting the highest ozone utilization rate of 0.081 min −1 . Multiple ROS quantification and contribution experiments jointly demonstrated that ZnOOH had an advantage over the other catalysts only n ·OH generation, but the·OH contributed 93 % of target removal in the ZnOOH/O 3 process. Structure analysis of ZnOOH suggested that its·OH generation had little connection with the contents of surface metal and adsorbed water, but was dependent on the surface structural hydroxyl that would undergo loss at 100–300℃. This concentration of ZnOOH was 10.1 mM/g, which was 1.7, 5.3, and 6.3 times higher than that of FeOOH, CoOOH, and MnOOH, respectively. Heat treatment further revealed that these surface hydroxyl mainly originated from the hydroxyl ions from water dissociation and could regenerate timely during reuse. Finally, a possible catalysis pathway was proposed.
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