CuSn Double‐Metal Hydroxides for Direct Electrochemical Ammonia Oxidation to Dinitrogen

Abstract

Direct electrochemical ammonia oxidation reaction (dAOR) to form N2 is of great significance to process ammonia‐containing wastewater or to make efficient ammonia fuel cells. Herein, CuSn double‐metal hydroxides are synthesized via a co‐precipitation method and used in dAOR with 10 mM normalNnormalH3 −N Among the synthesized hydroxides, CuSn(OH)6 shows a decent N2 −N partial current density (1.2 mA cm−2) and a substantially higher N2 −N Faradaic efficiency (84.5 %). In situ infrared spectroscopy confirms that the intermediacy of normalN2normalHnormaly dimeric species facilitates the formation of desired N2 product during the dAOR process. The synergy between Cu and Sn is critical for the enhanced dAOR activity, as Cu serves as the catalytic center while Sn adsorbs normalNnormalH3 −N intensively.

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

“…Notably, Fe2O3(104) has the highest activity, and NO adsorption was stronger on this surface than on H. Although it was thought that Fe2O3(012) had little effect on NO reduction due to the endothermic NO adsorption step, the H adsorption on Fe2O3(012) was weaker than that of NO. Furthermore, the adsorption of H on Fe2O3 (110) was stronger than that of NO. The integrated crystal orbital Hamilton population results (Fig.…”

“…Except for Pt and Pt-based catalysts, high AOR activities were also observed on Ti/IrO2-RuO2 [100], Ni2P/Ni foam (NiOOH as the real active species) [101], NiCu/carbon paper (CP) [102], NiCu/boron-doped diamond (BDD) [103], Ni0.8Cu0.2 oxyhydroxide [104], Ni(OH)2/NiOOH/Ni foam [105], NiCo oxide composite/Ni foam [106], high-entropy (MnFeCoNiCu)3O4 [107], Fe/FeNx [108], NiCo2N nanosheets (electrolyte: NH3 saturated 0.1 M KPF6 acetonitrile solution) [109], and CuSn(OH)6 nanorods (CuOOH as the real active species) [110]. According to these reports, it is clear that Pt-, Ni-, and Cu-based materials all possess good AOR performance in practice.…”

“…When compared with many recent NORR catalysts, our Fe2O3 catalyst has the following advantages: (1) It can be prepared easily on a large scale as the most common transition metal oxide; (2) NO reduction to NH3 with Fe-based heterogeneous catalysts held great promise to enable cost effective NH3 electrosynthesis, as Fe is an incredibly low-cost element; (3) it achieved relatively large NH3 FEs with good operation stability; (4) our Fe2O3 catalyst effectively suppressed the unwanted HER; (5) the close contact with Fe2O3 and substrate aided flow of electrons toward NO and intermediates. Theoretical calculations revealed that NO can be easily adsorbed on different Fe2O3 crystal planes (i.e., Fe2O3 (104) and Fe2O3 (110)) and the energy changes of the endothermic steps on the Fe2O3(104) surface were relatively small. Notably, Fe2O3(104) has the highest activity, and NO adsorption was stronger on this surface than on H. Although it was thought that Fe2O3(012) had little effect on NO reduction due to the endothermic NO adsorption step, the H adsorption on Fe2O3(012) was weaker than that of NO.…”

In situ decorated Cu2FeSnS4 nanosheet arrays for low voltage hydrogen production through the ammonia oxidation reaction

“…There is a significant increase in the anodic current density of the CFTS electrocatalysts, which implies enhanced electrochemical activity towards the AOR. 44 Among these, EG-CFTS shows relatively higher current density compared to the EtOH-CFTS and DI-CFTS electrocatalysts. Besides, in the presence of ammonia, the CV curves appeared to shift toward the negative scale in comparison to those of the absolute KOH electrolyte in Fig.…”

“…Cu and Sn sites are imposed as active elements for ammonia dissociation, and consequently, Fe sites promote conductivity, facilitating effective AOR performances in the prepared CFTS electrocatalysts. 44,47 Besides, Fig. 4c and d show linear sweep voltammetry (LSV) carried out to investigate the OER and AOR performance of all the prepared CFTS electrocatalysts in 1 M KOH and the mixed aqueous solution of 1 M KOH and 0.5 M NH 4 OH, respectively.…”