Raney nickel coupled nascent hydrogen as a novel strategy for enhanced reduction of nitrate and nitrite.

Raney nickel (R-Ni) is a cost-effective hydrogenation catalyst, and nascent hydrogen (Nas-H) generated in situ on the cathode trends to more reactive than commercial hydrogen (Com-H). In the present work, nitrate and nitrite (NO) reduction via R-Ni/Nas-H catalytic system was investigated. The results show that hydrogenation of NO (C = 3.0 mM) follows pseudo-first-order reaction kinetics with kinetic constants of 5.18 × 10 min (NO) and 6.46 × 10 min (NO). The saturation demand for Nas-H is only 0.8 mL min at a fixed R-Ni dosage of 1.0 g L. The experiments reveal that both Nas-H and hydrogen adatoms (H∗) can drive the reduction of NO. The improved reduction ratios of NO are attributed to two aspects: (1) the micro/nano-sized Nas-H bubbles exhibits increased reactivity due to the fine dispersion of the hydrogen molecules; (2) the alkaline environment formed by the cathode positively maintain R-Ni activity, thus, Nas-H bubbles were more readily activated to generate powerful H∗. The results give insight into NO hydrogenation via introducing fine hydrogen resource, and can develop an efficient catalytic hydrogenation technique without noble metals.