Schottky Barrier-Induced Surface Electric Field Boosts Universal Reduction of NOx- in Water to Ammonia

NOx- reduction acts a pivotal part in sustaining globally balanced nitrogen cycle and restoring ecological environment, ammonia (NH3) is an excellent energy carrier and the most valuable product among all the products of NOx- reduction reaction, the selectivity of which is far from satisfaction due to the intrinsic complexity of multiple-electron NOx--to-NH3 process. Here, we utilize the Schottky barrier-induced surface electric field, by the construction of high density of electron-deficient Ni nanoparticles inside nitrogen-rich carbons, to facilitate the enrichment and fixation of all NOx- anions on the electrode surface, including NO3- and NO2-, and thus ensure the final selectivity to NH3. Both theoretical and experimental results demonstrate that NOx- anions were continuously captured by the electrode with largely enhanced surface electric field, providing excellent Faradaic efficiency of 99 % from both electrocatalytic NO3- and NO2- reduction. Remarkably, the NH3 yield rate could reach the maximum of 25.1 mg h(-1) cm(-2) in electrocatalytic NO2- reduction reaction, outperforming the maximum in the literature by a factor of 6.3 in neutral solution. With the universality of our electrocatalyst, all sorts of available electrolytes containing NOx- pollutants, including seawater or wastewater, could be directly used for ammonia production in potential through sustainable electrochemical technology.

Automated summary

The study utilizes a Schottky barrier-induced surface electric field to improve the selectivity of NH3 production in NOx reduction reactions, achieving a high Faradaic efficiency of 99% for both electrocatalytic NO3- and NO2- reduction. Experimental results show that the NH3 yield rate can reach a maximum of 25.1 mg h(-1) cm(-2), outperforming existing literature by a factor of 6.3, demonstrating great practical value.