Development of the Ambient Green Ammonia by Three Routes

In industry, NH 3 is usually produced by the Haber-Bosch process, a synthesis technology that has been indispensable to human society for over a century. Still, the method operates at high temperatures (400-500°C) and high pressures (15-25 MPa). It consumes a large amount of hydrogen produced by fossil-fuel steam reforming to react with nitrogen, which requires more energy and has a high social cost due to its carbon footprint. In recent years, we have explored green ammonia production through photocatalytic and electrocatalytic N 2 reduction (PNRR vs. eNRR) and electrocatalytic NO 3 - reduction (eNO3RR). The 1% Ag-BiMn-based oxysulfide photocatalyst for PNRR achieved a high yield of ~3 mmol/g.h, but its yield remains much lower than the photo-H 2 yield. eNO3RR with a CuCo-based oxide/sulfide catalyst prepared by a hydrothermal route can yield above 44.6 mg/h.cm 2 with a single-stack cell. eNRR with a CuBi-based sulfur-oxide catalyst synthesized on a Ni foam by a chemical process can yield above 3.0 mg/h.cm 2 with an H-type cell. The yield rate follows the order: PNRR < eNRR < eNO3RR after laboratory self-calibration. PNRR and eNRR involve an inert, triple-bonded, non-polar N2 reactant, making their reactions challenging. The reaction micromechanisms are investigated.