Efficient electrochemical NO reduction to NH over metal-free g-CN nanosheets and the role of interface microenvironment.

The ever-increasing NO emission has caused severe environmental issues and adverse effects on human health. Electrocatalytic reduction is regarded as a win-win technology for NO treatment with value-added NH generation, but the process is mainly relied on the metal-containing electrocatalysts. Here, we developed metal-free g-CN nanosheets (deposited on carbon paper, named as CNNS/CP) for NH synthesis from electrochemical NO reduction under ambient condition. The CNNS/CP electrode afforded excellent NH yield rate of 15.1 μmol h cm (2180.1 mg g h) and Faradic efficiency (FE) of ∼41.5 % at - 0.8 and - 0.6 V, respectively, which were superior to the block g-CN particles and comparable to the most of metal-containing catalysts. Moreover, through adjusting the interface microenvironment of CNNS/CP electrode by hydrophobic treatment, the abundant gas-liquid-solid triphasic interface improved NO mass transfer and availability, which enhanced NH production and FE to about 30.7 μmol h cm (4424.2 mg g h) and 45.6 % at potential of - 0.8 V. This study opens a novel pathway to develop efficient metal-free electrocatalysts for NO electroreduction and highlights the importance of electrode interface microenvironment in electrocatalysis.