The efficient electrocatalytic and photocatalytic reduction of nitric oxide into ammonia over 0D/3D g-C3N4 quantum dots/3DOMM-TiO2-x heterojunction

An appealing strategy for air pollution treatment is the conversion of NOx in flue gas to valuable chemicals in ambient conditions. The electrocatalytic reduction of nitric oxide has been demonstrated to be a very effective process, however, the photocatalytic reduction of nitric oxide hasn't received much research attention. Herein, we developed a novel 0D/3D g-C3N4 QDs/3DOMM-TiO2-x catalyst, and investigated its performances in both electro- and photocatalytic reduction of nitric oxide to ammonia through experimental analysis and theoretical computation. In the electrocatalytic reduction of NO, the NH3 yield of g-C3N4 QDs/3DOMM-TiO2-x is up to 3841.5 μg h−1 mg−1, which is 15.15, 3.14, and 1.15 times that of TiO2 (P25), 3DOMM-TiO2 and g-C3N4 QDs/3DOMM-TiO2, respectively. The best reaction pathway is *NO → *HNO → *HNOH → *NH→ *NH2 → *NH3 → *NH4+, and the potential determining step is *NH → *NH2. Furthermore, the NH3 yield is estimated to be 95.07 μg h−1 mg−1 in the photocatalytic reduction of NO, using g-C3N4 QDs/3DOMM-TiO2-x as single photoelectrode. The NO molecules are reduced to NH3 on the CB of the g-C3N4 QDs by the accumulated photoelectrons, and charge migration occurs according to the S-scheme in the g-C3N4 QDs/3DOMM-TiO2-x photocatalyst. The results pave a new route for producing ammonia from NO under ambient conditions using electricity and solar energy.