Na Zhou,Jiazhi Wang,Ning Zhang,Zhi Wang,Hengguo Wang,Gang Huang,Di Bao,Haixia Zhong,Xinbo Zhang
Electrochemical conversion of nitrate (NO 3 − ) pollutants into chemical feedstock and fuel ammonia (NH 3 ) can contribute to sustainable mitigation of the current severe energy and environmental crises. However, the electrocatalytic NO 3 − reduction to NH 3 (NRA) involves a sluggish multielectron and proton transfer process that competes with the hydrogen evolution reaction (HER) in aqueous media, imposing great challenges in developing highly selective catalysts for NRA. In this study, we developed a copper and copper-tetracyanoquinodimethane composite catalyst (Cu@CuTCNQ), which possesses a high density of copper vacancy defects. This catalyst has been proven to be efficient for NRA through an in situ electrochemical reconstruction method. The structural evolution of CuTCNQ during NRA was investigated by in situ Raman spectroscopy, which indicated an accelerated charge transfer from the CuTCNQ substrate to the derived Cu, which facilitated the adsorption activation of NO 3 − . The obtained Cu@CuTCNQ exhibited an excellent catalytic performance for NRA, with a Faradaic efficiency of 96.4% and productivity of 144.8 μmol h −1 cm −2 at −0.6 V vs . a reversible hydrogen electrode, superior to Cu nanoparticle counterparts and most Cu-based catalysts. Cu vacancy defects and sufficient interfacial charge transfer synergistically optimize the charge distribution of Cu active sites, reduce the energy barrier for NO 3 − adsorption, and promote deoxidation and hydrogenation processes, thus enhancing NRA and selectivity.
The discharge of colorless and water-soluble formaldehyde (FA) wastewater poses a serious threat to human health. In this study, copper based Fenton-like catalyst Cu x S y was innovatively introduced into the FA degradation system. Cu x S y catalysts with different morphologies were regulated by ethylenediamine . The Cu 7 S 4 catalyst exhibited 99% degradation performance towards FA. The physical and chemical properties of catalysts indicate that the Cu 7 S 4 catalyst has a beautiful dendritic snowflake like structure, which is more conducive to the adsorption and degradation process of FA. Electron paramagnetic resonance (EPR) detected an obvious Cu defect (g=2.064) in Cu 7 S 4 , which can effectively activate H 2 O 2 and stimulate the generation of •OH, thus accelerating the degradation of FA. Compared with Fenton reagent, Cu 7 S 4 shows more than 75% FA degradation performance (pH=5 and pH=9). Further research showed that the H 2 O 2 :Cu 7 S 4 ratio of 2:10 showed a 95% degradation effect on FA at 200–1000 ppm, demonstrating a more efficient and stable FA degradation ability. Moreover, the mechanism of FA degradation was analyzed.
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