Electrochemically converting NO 3 À into NH 3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO 3 À is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO 3 À reduction reaction (NO 3 RR) with dilute NO 3 À concentration (� 100 ppm NO 3 À À N). Notably, a linear relationship was established by plotting NH 3 yield vs. the oxidation state of Cu, indicating that the increase of Cu + content leads to an enhanced NO 3 À -to-NH 3 conversion activity. Under a low NO 3 À À N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO 3À -to-NH 3 conversion at À 0.55 to À 0.6 V vs. RHE, and a record-high NH 3 yield of 309 mmol h À 1 g cat À 1 , which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h À 1 g cat À 1). This research provides an effective method for conversion of dilute NO 3 À to NH 3 , which has certain guiding significance for the efficient and green conversion of wastewater in the future.

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Powered by clean and renewable energy, electrocatalytic CO 2 reduction reaction (CO 2 RR) to chemical feedstocks is an effective way to mitigate the greenhouse effect and artificially close the carbon cycle. However, the performance of electrocatalytic CO 2 RR was impeded by the strong thermodynamic stability of CO 2 molecules and the high susceptibility to hydrogen evolution reaction (HER) in aqueous phase systems. Moreover, the numerous reaction intermediates formed at very near potentials lead to poor selectivity of reaction products, further preventing the industrialization of CO 2 RR. Catalysis in confined space can enrich the reaction intermediates to improve their coverage at the active site, increase local pH to inhibit HER, and accelerate the mass transfer rate of reactants/products and subsequently facilitate CO 2 RR performance. Therefore, we summarize the research progress on the application of the confinement effects in the direction of CO 2 RR in theoretical and experimental directions. We first analyzed the mechanism of the confinement effect. Subsequently, the confinement effect was discussed in various forms, which can be characterized as an abnormal catalytic phenomenon due to the relative limitation of the reaction region. In specific, based on the physical structure of the catalyst, the confinement effect was divided in four categories: pore structure confinement, cavity structure confinement, active center confinement, and other confinement methods. Based on these discussions, we also have summarized the prospects and challenges in this field. This review aims to stimulate greater interests for the development of more efficient confined strategy for CO 2 RR in the future.

Research advances in the application of confinement effects towards the electrocatalytic CO2 reduction reaction (CO2RR) in theoretical and experimental directions are summarized. Confinement effects were divided into four categories: pore structure confinement, cavity structure confinement, active center confinement, and other confinements. At the end of this Review, the prospects and challenges in this field are outlined. More information can be found in the Review by Fengshou Yu, Lu‐Hua Zhang et al.

Electrochemically converting NO 3 À into NH 3 offers a promising route for water treatment. Nevertheless, electroreduction of dilute NO 3 À is still suffering from low activity and/or selectivity. Herein, B as a modifier was introduced to tune electronic states of Cu and further regulate the performance of electrochemical NO 3 À reduction reaction (NO 3 RR) with dilute NO 3 À concentration (� 100 ppm NO 3 À À N). Notably, a linear relationship was established by plotting NH 3 yield vs. the oxidation state of Cu, indicating that the increase of Cu + content leads to an enhanced NO 3 À -to-NH 3 conversion activity. Under a low NO 3 À À N concentration of 100 ppm, the optimal Cu(B) catalyst displays a 100 % NO 3À -to-NH 3 conversion at À 0.55 to À 0.6 V vs. RHE, and a record-high NH 3 yield of 309 mmol h À 1 g cat À 1 , which is more than 25 times compared with the pristine Cu nanoparticles (12 mmol h À 1 g cat À 1). This research provides an effective method for conversion of dilute NO 3 À to NH 3 , which has certain guiding significance for the efficient and green conversion of wastewater in the future.