Electrocatalytic\nReduction of Nitrate to Ammonia in\nan Aqueous Environment Using Nanoporous N- and P‑Enriched Carbonaceous\nMaterial

Carbonization (Argon atmosphere, 900 °C, 2 h) of\nheteroatom-enriched\npyridine-bridged inorganic–organic hybrid material (HPHM) resulted\nin the formation of a high specific surface area (SA<sub>BET</sub> of 1080 m<sup>2</sup> g<sup>–1</sup>) carbonaceous material\ndesignated as HPHMC900. The HPHMC900 serves as an effective electrocatalyst\nfor the reduction of nitrate in an aqueous environment to ammonia\n(NO<sub>3</sub>RR). Importantly, HPHMC900 demonstrated fast kinetics\nfor the NO<sub>3</sub>RR with a low Tafel slope of 70 mV decade<sup>–1</sup>. An NH<sub>3</sub> production yield of 21 μg\nh<sup>–1</sup> mg<sub>cat</sub><sup>–1</sup> was obtained\nwith a Faradaic efficiency (FE) of 88.3% at −0.4 V in a 0.1\nM KNO<sub>3</sub> electrolytic solution. The high double layer capacitance\n(<i>C</i><sub>dl</sub>) of 14.1 mF cm<sup>–2</sup> corroborates high SA<sub>BET</sub> and exposed active sites of HPHMC900.\nThe maximum FEs were estimated to be 48%, 93%, and 98%, corresponding\nto 0.05, 0.5, and 1.0 M KNO<sub>3</sub> with maximum NH<sub>3</sub> production yields of 18.7, 22.1, and 39.0 μg h<sup>–1</sup> mg<sub>cat</sub><sup>–1</sup>, respectively. The potential\nof employing HPHMC900 for the NO<sub>3</sub>RR as an electrocatalyst\nis evident by its robust stability, high SA<sub>BET</sub>, and enrichment\nwith heteroatoms N (7.7%) and P (0.28%). Thus, this sustainable environmentally\nbenign strategy can be used for the treatment of pollutant NO<sub>3</sub><sup>–</sup> to produce NH<sub>3</sub>.