Synthesis of electrocatalyst from electroplating sludge for efficient N2 reduction under ambient conditions

Abstract

Electroplating sludge (ES) is a solid waste, which is rich in transition-metal content. However, ES is usually treated or disposed, instead of recycling. For the first time, this work synthesized an electrocatalyst from ES, and applied it in catalytic Nitrogen reduction reaction (NRR) to produce ammonia under ambient conditions. As a result, the ES-derived catalyst showed the highest ammonia yield of 15.9 μg h−1 mg−1cat, which was far bigger than that (9.8 μg h−1 mg−1cat) of a pure-reagent-synthesized control. Faraday efficiency of the ES-derived catalyst reached the maximum of 0.83% at −0.9 V, obviously lower that of the control. Moreover, chronoamperometry curves of the ES-derived catalyst showed little fluctuate after 5 cycles, indicating a good stability. After detailed characterizations, following advantages were attributed to the enhanced performance. The ES-derived catalyst was doped by Fe and Mg (doping amount = 21% molar ratio). It owned a bigger percentage of oxygen vacancy (16%) than the control (12%). Besides, it had the bigger specific surface area, and enhanced binding energy/capacity for N2. The electrocatalytic NRR was carried out by distal and alternating pathways. After all, the main result of this work was in favor of producing high-value-added products by recycling of industrial wastes.