Raney nickel coupled nascent hydrogen as a novel strategy for enhanced reduction of nitrate and nitrite
2021
Wang, Weilai | Wang, Kaixuan | Xu, Lei | Li, Yang | Niu, Junfeng
Raney nickel (R–Ni) is a cost-effective hydrogenation catalyst, and nascent hydrogen (Nas-H₂) generated in situ on the cathode trends to more reactive than commercial hydrogen (Com-H₂). In the present work, nitrate and nitrite (NOX⁻) reduction via R–Ni/Nas-H₂ catalytic system was investigated. The results show that hydrogenation of NOX⁻ (C₀ = 3.0 mM) follows pseudo-first-order reaction kinetics with kinetic constants of 5.18 × 10⁻² min⁻¹ (NO₃⁻) and 6.46 × 10⁻² min⁻¹ (NO₂⁻). The saturation demand for Nas-H₂ is only 0.8 mL min⁻¹ at a fixed R–Ni dosage of 1.0 g L⁻¹. The experiments reveal that both Nas-H₂ and hydrogen adatoms (Hₐdₛ∗) can drive the reduction of NOX⁻. The improved reduction ratios of NOX⁻ are attributed to two aspects: (1) the micro/nano-sized Nas-H₂ 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-H₂ bubbles were more readily activated to generate powerful Hₐdₛ∗. The results give insight into NOX⁻ hydrogenation via introducing fine hydrogen resource, and can develop an efficient catalytic hydrogenation technique without noble metals.
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