Experimental and theoretical investigation on facet-dependent MoO2/BiOBr Z-scheme heterojunction photocatalytic nitrogen reduction: modulation of bulk charge separation efficiency by built-in electric field intensity

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 12; no. 27; pp. 16877 - 16891
• Main Authors: Chen, Zhuying, Huang, Zhiling, Yang, Jieyi, Meng, Yue, Xie, Bo, Ni, Zheming, Xia, Shengjie
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 09.07.2024
• Subjects: Ammonia; Charge efficiency; Efficiency; Electric charge; Electric field strength; Electric fields; Heterojunctions; Nitrogen; Photocatalysis; Potential energy; Separation
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d4ta02394c

Based on facet engineering and Z-scheme heterojunctions, a series of MoO2/BiOBr Z-scheme heterojunctions with different facet ratios of (102)/(001) were prepared for photocatalytic nitrogen reduction. The performance of nitrogen reduction is greatly improved after constructing heterojunctions, and the activity increases rapidly with the increase of the (102)/(001) ratio of BiOBr in the heterojunction. MoO2/BiOBr-0 with a (102)/(001) ratio of 0.167 exhibits the highest activity, reaching 176.66 μmol g−1 h−1, which is 4–5 times higher than that of pristine MoO2 and BiOBr. Based on the built-in electric field (BIEF) strength, bulk charge separation (BCS) efficiency, and theoretical calculation of the materials, it is believed that due to the increase in the (102)/(001) facet ratio, the BIEF strength between the two phases of the heterojunction is enhanced, resulting in a high BCS efficiency. This promotes more surface enriched photo-generated electrons to act on nitrogen reduction, thereby achieving efficient photocatalytic ammonia synthesis. According to DFT, compared to MoO2 and BiOBr, MoO2/BiOBr not only adsorbs N2 more strongly than H, but also ΔGmax in the potential energy determination step (PDS) is lower, thus exhibiting superior NRR activity. The calculation is completely consistent with the experimental results, further confirming that the construction of Z-scheme heterojunctions with a high proportion of (102) facets greatly promotes the performance of MoO2 and BiOBr in catalyzing nitrogen reduction.