Direct Z-scheme photocatalytic nitrogen reduction to ammonia with water in metal-free BC4N/aza-CMP heterobilayer

• Published in: Science China materials 2023-11, Vol.66 (11), p.4377-4386
• Main Authors: Fan, Yingcai, Zhang, Zhihua, Wang, Juan, Ma, Xikui, Zhao, Mingwen
• Format: Article
• Language: English
• Subjects: Ammonia; Chemical bonds; Chemical reduction; Chemical synthesis; Chemistry and Materials Science; Chemistry/Food Science; Current carriers; Density functional theory; Energy gap; Energy levels; Materials Science; Molecular dynamics; Nitrogen; Nitrogenation; Oxygen evolution reactions; Photocatalysis; Photocatalysts; Redox reactions; Separation; Solar energy
• ISSN: 2095-8226; 2199-4501
• DOI: 10.1007/s40843-023-2587-7

Photocatalytic ammonia (NH 3 ) synthesis from air and water without external energy input or sacrificial agents is an attractive approach for nitrogen fixation. However, finding a suitable photocatalyst with strong optical absorption, efficient photogenerated carrier separation, and adequate driving force (potentials of photoinduced carriers) to trigger the nitrogen reduction reactions (NRRs) and oxygen evolution reactions (OERs) simultaneously is challenging. Herein, we propose a direct Z-scheme photocatalytic system based on a two-dimensional metal-free BC 4 N/aza-CMP heterobilayer. The results of density functional theory and time-dependent ab initio nonadiabatic molecular dynamics reveal that the photoexcited carriers in the BC 4 N/aza-CMP heterobilayer follow a Z-scheme migration route, leading to the efficient charge carrier separation and spatially separated reaction sites for NRR (BC 4 N layer) and OER (aza-CMP layer). Moreover, the appropriate band gaps and energy levels of the BC 4 N/aza-CMP heterobilayer enable efficient solar energy capture and provide sufficient driving force (1.01 V for NRR and 2.11 V for OER) to initiate the redox reactions. Additionally, the activation of the N≡N bond by B atoms in the BC 4 N layer promotes the sequential hydrogenation of N atoms and reduces the overpotential of NRR. Consequently, the NRR and OER can proceed spontaneously, driven by photogenerated carriers with no need for sacrificial agents. The predicted maximum value of solar-to-chemical efficiency is 7.59%. This work will be an important reference for the rational design of direct Z-scheme photocatalysts for NRR and promote the development of solar-driven NH 3 synthesis.