Electro-triggered Joule heating method to synthesize single-phase CuNi nano-alloy catalyst for efficient electrocatalytic nitrate reduction toward ammonia

Electrochemical nitrate reduction reaction (NO 3 RR) has great potential for ammonia (NH 3 ) synthesis benefiting from its environmental friendliness and sustainability. Cu-based alloys with elemental diversity and adsorption tunability are widely used as electrocatalyst to lower the reaction overpotential for NO 3 RR catalysis. However, phase separation commonly found in alloys leads to uneven distribution of elements, which limits the possibility of further optimizing the catalytic activity. Herein, an electro-triggered Joule heating method, possessing unique superiority of flash heating and cooling that lead to well-dispersed nanoparticles and uniform mixing of various elements, was adopted to synthesize a single-phase CuNi nano-alloy catalyst evenly dispersed on carbon fiber paper, CFP-Cu 1 Ni 1 , which exhibited a more positive NO 3 RR initial potential of 0.1 V versus reversible hydrogen electrode (vs. RHE) than that of pure copper nanoparticles at 10 mA·cm −2 in 0.5 mol·L −1 Na 2 SO 4 + 0.1 mol·L −1 KNO 3 solution. Importantly, CFP-Cu 1 Ni 1 presented high electrocatalytic activity with a Faradaic efficiency of 95.7% and NH 3 yield rate of 180.58 µmol·h −1 ·cm −2 (2550 µmol·h −1 ·mg cat −1 ) at −0.22 V vs. RHE. Theoretical calculations showed that alloying Cu with Ni into single-phase caused an upshift of its d-band center, which promoted the adsorption of NO 3 − and weakened the adsorption of NH 3 . Moreover, the competitive adsorption of hydrogen ions was restrained until −0.24 V. This work offers a rational design concept with clear guidance for rapid synthesis of uniformly dispersed single-phase nano-alloy catalyst for efficient electrochemical NO 3 RR toward ammonia.