Rational design of cocatalyst for highly improved ammonia production from photoelectrochemical nitrate reduction

• Published in: Applied catalysis. B, Environmental Environmental, 2024-08, Vol.351, p.123980, Article 123980
• Main Authors: Liu, Di, Peng, Shuyang, Qiao, Lulu, Bai, Haoyun, An, Keyu, Liu, Chunfa, Chen, Mingpeng, Lo, Kin Ho, Ng, Kar Wei, Peng, Shengjie, Wang, Shuangpeng, Ip, Weng Fai, Pan, Hui
• Format: Article
• Language: English
• Subjects: Ammonia production; DFT calculations; Nitrate reduction; Photoelectrocatalysis
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2024.123980

Photoelectrochemical nitrate reduction reaction (p-NO3RR) has been one of the most promising ways for ambient ammonia synthesis. However, current trials haven’t realized efficient ammonia production due to low ammonia yield. Herein, we present that silicon (Si) photocathode with CoNi as co-catalyst can achieve low onset potential, high ammonia yield, and close-to-unity selectivity in p-NO3RR. The optimal photocathode (Co0.95Ni0.05/Si) exhibits a record-high ammonia yield of 2054 µg h−1 cm−2 with an excellent Faraday efficiency (FE) of 98.6% at only −0.1 V vs. reversible hydrogen electrode (RHE), which outperforms reported photocathodes in literature. Our characterizations and calculations demonstrate that the metallic Co dominantly exists as the interior of Co0.95Ni0.05/Si that accelerates electron transfer, while Ni is introduced into Co3O4 on the surface that optimizes the adsorption behavior and improves the activity and selectivity. We believe that the findings provide insightful guidance for enhanced performance towards large-scale ammonia synthesis by photoelectrochemical nitrate reduction. [Display omitted] •The Co0.95Ni0.05/Si photocathode exhibits the highest ammonia yield among the reported photocathodes.•The Co0.95Ni0.05/Si photocathode exhibits superior selectivity and stability for p-NO3RR.•The cocatalysts of Co0.95Ni0.05/Si show a core-shell structure, where the metallic Co exists in the interior, while Ni-incorporated Co3O4 is on the surface.•The catalytic mechanism for Co0.95Ni0.05/Si photocathode was surveyed.