Ni2P nanosheet array for high-efficiency electrohydrogenation of nitrite to ammonia at ambient conditions.

Abstract Ammonia (NH3) plays an important role in agriculture and industry. The industry-scale production mainly depends on the Haber-Bosch process suffering from issues of environment pollution and energy consumption. Electrochemical reduction can degrade nitrite (NO2–) pollutants in the environment and convert it into more valuable NH3. Here, Ni2P nanosheet array on nickel foam is proposed as a 3D electrocatalyst for high-efficiency electrohydrogenation of NO2– to NH3 under ambient reaction conditions. When tested in 0.1 M phosphate buffer saline with 200 ppm NO2–, such Ni2P/NF is able to obtain a large NH3 yield rate of 2692.2 ± 92.1 μg h–1 cm–2 (3282.9 ± 112.3 μg h–1 mgcat.–1), a high Faradic efficiency of 90.2 ± 3.0%, and selectivity of 87.0 ± 1.7% at –0.3 V versus a reversible hydrogen electrode. After 10 h of electrocatalytic reduction, the conversion rate of NO2– achieves near 100%. The catalytic mechanism is further investigated by density functional theory calculations.