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

Ammonia (NH) 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 (NO) pollutants in the environment and convert it into more valuable NH. Here, NiP nanosheet array on nickel foam is proposed as a 3D electrocatalyst for high-efficiency electrohydrogenation of NO to NH under ambient reaction conditions. When tested in 0.1 M phosphate buffer saline with 200 ppm NO, such NiP/NF is able to obtain a large NH yield rate of 2692.2 ± 92.1 μg h cm (3282.9 ± 112.3 μg h mg), 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 NO achieves near 100%. The catalytic mechanism is further investigated by density functional theory calculations.