Heterojunction-enhanced electron transfer of copper nanoparticles promotes electrocatalytic ammonia synthesis from nitric oxide
LiWei Chen, Liying Zhang, Sen Qiao
Abstract
Electrocatalytic nitric oxide (NO) reduction to ammonia (NH 3 ) serves as an innovative approach that concurrently addresses two pressing challenges: sustainable NH 3 synthesis through renewable pathways and environmental detoxification of hazardous nitric oxide . While the thermodynamic driving force of the electrocatalytic NO-to-NH 3 conversion (NORR) favors NH 3 generation, the system’s practical viability is compromised by kinetically sluggish reaction pathways and the inherent solubility constraints of NO (1.93 mM in aqueous media at 25 ℃), with performance attenuation becoming progressively severe when the NO concentration decreases. However, an efficient copper-based catalyst that can effectively adsorb and activate NO is not yet available. Here, we have utilized the strategy of biphasic carriers to enhance MSI (metal-support interactions) to develop rutile-anatase titanium dioxide (TiO 2 ) heterojunction-supported copper nanoparticles (Cu@AR-TiO 2 ) as an effective catalyst for NORR. Under processing conditions of 10 % v/v NO, the NH 3 -Faraday efficiency reached 91.38 % at −0.7 V vs. RHE, with the NH 3 yield rate achieving 393.73 μmol h −1 mg -1 cat at −0.8 V vs. RHE, surpassing counterparts devoid of heterojunction or copper nanoparticles . X-ray photoelectron spectroscopy and X-ray absorption spectroscopy shows that the three-phase interface formed by rutile-anatase TiO 2 (AR-TiO 2 ) heterojunction with copper nanoparticles (Cu NPs) enhanced the MSI of Cu NPs with the carrier to effectively promote the electron transfer from Cu NPs to carriers to form electron-deficient copper. In-situ Raman coupled with NO temperature-programmed desorption experiments revealed that the distinctive electron structure of Cu@AR-TiO 2 (copper nanoparticles supported by AR-TiO 2 ) strengthened the adsorption of NO and facilitated the generation of·NH 3 (ammonia being absorbed) intermediate, ultimately achieving superior catalytic efficiency in NH 3 production. This provides a novel approach to the design of NO-to-NH 3 catalysts.