Photocatalytic nitrogen fixation (PNF) under mild conditions is a promising approach to sustainable ammonia (NH 3 ) synthesis. However, PNF normally encounters many challenges, such as inefficient charge separation, poorly exposed active sites, and sluggish multi-electron/proton-involved steps. Here, we design a step (S)-scheme WS 2-x /La 1 -WO 2.9 heterojunction through integrating rich oxygen/sulfur dual-vacancies and loading rare-earth La single atoms. The as-prepared photocatalyst achieves a high NH 3 generation rate of 124.9 μmol∙g −1 ∙h −1 , which is 4.4, 1.7 and 1.2-fold those of pristine WO 3-x , WS 2-x and WS 2-x /WO 2.9 , respectively. Further in-depth characterizations and theoretical calculations reveal a synergistic photocatalytic effect in WS 2-x /La 1 -WO 2.9 , mainly due to the regulated collaborative dual defects and a lower energy d −π* occupation orbital from the modulation of La-modified W site. This leads to significantly reducing the reaction barrier in the rate-limiting step and elucidating the key intermediate processes (-NH 2 , -NH 2 NH 2 ) of the nitrogen fixation reaction. Our study creates a comprehensive strategy, analogous to the “three birds with one stone” method, offering new insights into advancing PNF.
Leilei Yin,Mingzi Sun,Shuai Zhang,Yongkang Huang,Bolong Huang,Yaping Du
Currently, there are still obstacles to rationally designing the ligand fields to activate rare-earth (RE) elements with satisfactory intrinsic electrocatalytic reactivity. Herein, axial coordination strategies and nanostructure design are applied for the construction of La single atoms (La-Cl SAs/NHPC) with satisfactory oxygen reduction reaction (ORR) activity. The nontrivial LaN 4 Cl 2 motifs configuration and the hierarchical porous carbon substrate that facilitates maximized metal atom utilization ensure high half-wave potential (0.91 V) and significant robustness in alkaline media. The aqueous and flexible Zinc-air battery (ZAB) integrating La-Cl SAs/NHPC as the cathode catalyst exhibits a maximum power density of 260.7 and 68.5 mW cm −2 , representing one of the most impressive RE-based ORR electrocatalysts to date. Theoretical calculations have demonstrated that the Cl coordination evidently modulate the electronic structures of La sites, which promoted electron transfer efficiency by d-p orbital couplings. With enhanced electroactivity of La sites, the adsorptions of key intermediates are optimized to alleviate the energy barriers of the potential-determining step. Importantly, this preparation strategy is also successfully applied to other REs. This work provides perspectives for near-range electronic structure modulation of RE-SAs based on a nonplanar coordination micro-environment for efficient electrocatalysis.
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