Chen Yonghui,Zhao Jiafu,Song Mingzhu,Luo Shaojuan,Xie Shaoqu,Yan Kai
The development of safe, low-cost and highly active non-precious metal electrocatalysts plays a vital role in efficient hydrogen production. Herein, Mo 2 C/Mo 2 N heterostructure was in-situ synthesized by a two-step method for excellent hydrogen evolution performance at a universal pH range. The results show that the optimized MoCN-750-2h only needs 86.5, 102.5 and 120.5 mV overpotentials to reach 10 mA·cm −2 in alkaline, acidic and neutral media, respectively. Not only that, MoCN-750-2h had a low Tafel slope (37.2 and 88.5 mV·dec −1 ) in alkaline and neutral media, implying that catalytic kinetic is close to the level of Pt/C. These results can be attributed to reasonable C and N content in MoCN-750-2 h, optimizing the electron cloud distribution of Mo 2 C/Mo 2 N heterostructure to boost hydrogen production. Graphical Abstract MoCN heterostructure was in-situ synthesized by a two-step method for excellent hydrogen evolution performance at a universal pH range. The optimized electron cloud distribution of Mo 2 C/Mo 2 N would promote the formation of electron transfer channels, boosting the hydrogen evolution catalytic activity of the heterostructure. The MoCN heterostructure only needs 86.5,102.5 and 120.5 mV overpotentials to reach 10 mA·cm −2 in alkaline, acidic and neutral media, respectively. Not only that, MoCN-750-2 h had a low Tafel slope (37.2 and 88.5 mV·dec −1 ) in alkaline and neutral media, implying that catalytic kinetic is close to the level of Pt/C.
Constructing atomic-level cation vacancies is an effective strategy to modulate the electronic properties of host materials, thus promoting charge transfer and redox reaction kinetics. Herein, ultrathin Bi 24 O 31 Br 10 nanosheets with cationic vacancy was synthesized via an inventive precipitation strategy by adding appropriate arginine. The difunctional arginine can changes the pH of the synthetic system and selectively deprive Bi atoms on the surface to form Bi vacancies through strong affinity between functional groups and cations. The abundant Bi vacancy decrease the Gibbs free energy change and provide channels to promote bulk adsorption of Cr(VI), thus effectively reduces the carrier migration distance during in situ bulk photocatalytic reduction of Cr(VI) and induces the formation of new impurity states to improve the utilization of visible light. Bi vacancy mitigates strong excitonic effects confined by significantly reducing exciton binding energies, thus effectively promote the separation of photo-generated charges and suppress reorganization of photon-generated carrier. Benefiting from these merits, these exclusive V Bi -Bi 24 O 31 Br 10 ultra-thin nanosheets exhibit superior reduction performance for Cr(VI), and the removal rate was more than 90% at universal pH (2–10). This work provides a new idea for the construction of cation vacancies and a feasible method for the removal of Cr(VI) under alkaline conditions.
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