The most difficulty of efficient CO 2 electroreduction lies in the activation step that turns CO 2 into the CO 2 − radicals or other intermediates that can be further converted. To overcome this bottleneck, many efforts have been devoted to develop electrocatalysts to lower the overpotential of CO 2 activation, but they inevitably involve complicated or/and unscalable synthesis methods. Here we reported that the SO 4 2− ion modified metal foils, including Zn, Ag, Au and Cu, demonstrated ∼6.5, 1.4, 14 and 2.5 times of CO faradaic efficiency in K 2 SO 4 electrolyte compared to KHCO 3 electrolyte at −1.05 V vs. RHE. According to both experimental and DFT studies, the electron-rich metal-SO 4 adlayer can activate CO 2 by bending the linear molecule of CO 2 through donating electrons to the antibonding orbital of CO 2 , thus facilitating the formation of key intermediate *CO 2 − . Moreover, the adsorption of H + on metal sites is restrained by the metal-SO 4 adlayer, leading to a suppressed H 2 evolution activity. From a broader perspective, many catalysts can benefit from this approach to achieve more efficient CO 2 electrochemical reduction.
Yuling Ren,Pengfei Qi,Yinhua Wan,Chulong Chen,Xiangrong Chen,Shichao Feng,Jianquan Luo
A nanofiltration (NF) membrane with high salt permeation and high retention of small organics is appealing for the treatment of high-salinity organic wastewater. However, the conventional negatively charged NF membranes commonly show high retention of divalent anions (e.g., SO42–), and the reported positively charged NF membranes normally suffer super low selectivity for small organics/Na2SO4 and high fouling potential. In this work, we propose a novel “etching–swelling–planting” strategy assisted by interfacial polymerization and mussel-inspired catecholamine chemistry to prepare a mix-charged NF membrane. By X-ray photoelectron spectroscopy depth profiling and pore size distribution analysis, it was found that such a strategy could not only deepen the positive charge distribution but also narrow the pore size. Molecular dynamics confirm that the planted polyethyleneimine chains play an important role to relay SO42– ions to facilitate their transport across the membrane, thus reversing the retention of Na2SO4 and glucose (43 vs 71%). Meanwhile, due to the high surface hydrophilicity and smoothness as well as the preservation of abundant negatively charged groups (−OH and −COOH) inside the separation layer, the obtained membrane exhibited excellent antifouling performance, even for the coking wastewater. This study advances the importance of vertical charge distribution of NF membranes in separation selectivity and antifouling performance.
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