Emerging Atomically Engineered RuNi-Zn-ZIF-8 Catalyst for Remarkably High Electrocatalytic Nitrate Reduction to...

Here, we report an atomic substitution strategy between RuNi-Alloy and ZIF-8 to synthesize Ni single-atom catalyst (SAC) supported on a carbon-nitrogen framework (CNF), derived via high temperature calcination (900°C) of RuNi-ZIF-8. The resulting atomically engineered (RuZn)/Ni-CN exhibits multifunctional activity for both Nitrate reduction reaction (NO₃RR) and Oxygen evolution reaction (OER). In NO₃RR, (RuZn)/Ni-CN delivers a high ammonia yield of 10199 µg h^-1 mg^-1 _cat with 84% Faradaic efficiency (FE) at -0.9 V vs. RHE. This performance is obtained using a Pt anode in a 0.1 M NaNO₃ solution containing 0.1 m Na₂SO₄, following the optimization of pH. (RuZn)/Ni-CN achieves superior OER performance, with an overpotential of 303 mV at 50 mA cm^-2 and exhibits low charge transfer resistance (0.43 Ω) and a small Tafel slope (62 mV/dec), indicating fast reaction kinetics. The TOF reaches 0.3278 × 10^-3 s^-1 and retains long-term operational stability with negligible degradation for 30 h. (RuZn)/Ni-CN acted as a bifunctional catalyst in cathode and anode and delivered highest ammonia yield and FE of 10123 µg h^-1 mg^-1 _cat and 83%, respectively. EXAFS and structural analyses confirm strong metal-support interactions, with Ni as coordinatively unsaturated single atoms and minor clusters that synergistically enhance activity.