Polystyrene spheres-templated mesoporous carbonous frameworks implanted with cobalt nanoparticles for highly efficient electrochemical nitrate reduction to ammonia

• Published in: Applied catalysis. B, Environmental Environmental, 2023-04, Vol.323, p.122192, Article 122192
• Main Authors: Xu, Suxian, Shi, Yongbin, Wen, Zhibing, Liu, Xiao, Zhu, Yong, Liu, Guoquan, Gao, Hua, Sun, Licheng, Li, Fei
• Format: Article
• Language: English
• Subjects: Co nanoparticles; Heterogeneous electrocatalysis; Hierarchically porous carbon skeleton; in-situ Raman; Nitrate reduction reaction
• ISSN: 0926-3373; 1873-3883; 1873-3883
• DOI: 10.1016/j.apcatb.2022.122192

Electrocatalytic nitrate reduction reaction (eNO3RR) to ammonia (NH3) provides an intriguing approach for both environmental denitrification and sustainable NH3 synthesis. Herein, we report the fabrication of hierarchically mesoporous Co nanoparticles decorated N-doped carbon composites as a highly efficient electrocatalyst for eNO3RR by using monodispersed polystyrene spheres (PS) as sacrificial templates (MR Co-NC). By taking advantage of the large specific area of the pore-rich structures and the high intrinsic activity of metallic Co, the MR Co-NC shows remarkable activity toward eNO3RR, which achieves a partial current density of 268 mA cm−2 with a Faradaic efficiency (FE) of 95.35 ± 1.75 % and a generation rate of 1.25 ± 0.023 mmol h−1 cm−2 for NH3 production under the optimal conditions. The porous carbon skeleton was found to play a dual role by simultaneously protecting the active sites from oxidation and facilitating long-range charge and mass transfer. Theoretical calculations reveal a lower energy barrier of the rate-determining step (*NO2 + H2O + 2e- → *NO + 2OH-) on the metallic Co of MR Co-NC over β-Co(OH)2 formed by the reconstruction of carbon-free Co nanoparticles. [Display omitted] ●A mesopore-rich Co-NC electrocatalyst was fabricated by using PS as the sacrificial template.●The catalyst shows an extremely high NH3 yield rate (1.25 mmol h−1 cm−2) with the current density exceeding 200 mA cm−2.●The abundant hierarchical mesopores expedite mass transport and electron transfer.●The carbon skeleton prevents the active metal sites from reconstruction in alkaline solution.