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Polymeric carbon nitride coupled with a molecular thiomolybdate catalyst: exciton and charge dynamics in light-driven hydrogen evolution
Sustainable Energy & Fuels ( IF 5.6 ) Pub Date : 2020-10-12 , DOI: 10.1039/d0se01366h
Ashwene Rajagopal 1, 2, 3, 4 , Elham Akbarzadeh 1, 2, 3, 4, 5 , Chunyu Li 4, 6, 7, 8, 9 , Dariusz Mitoraj 2, 3, 4, 10 , Igor Krivtsov 2, 3, 4, 10 , Christiane Adler 2, 3, 4, 10 , Thomas Diemant 2, 3, 4, 11 , Johannes Biskupek 2, 4, 12, 13, 14 , Ute Kaiser 2, 4, 12, 13, 14 , Changbin Im 2, 3, 4, 10 , Magdalena Heiland 1, 2, 3, 4 , Timo Jacob 2, 3, 4, 10, 15 , Carsten Streb 1, 2, 3, 4, 15 , Benjamin Dietzek 4, 6, 7, 8, 9 , Radim Beranek 2, 3, 4, 10
Affiliation  

Solar hydrogen evolution from water is a necessary step to overcome the challenges of rising energy demand and associated environmental concerns. Low-cost photocatalytic architectures based on polymeric light absorbers coupled to highly efficient molecular catalysts might represent an attractive platform to address this issue. However, to-date, our mechanistic knowledge of these systems is still largely underdeveloped. In this study, a molecular molybdenum sulfide hydrogen evolving catalyst, [Mo3S13]2−, is loaded onto polymeric carbon nitride (CNx) photoabsorber by impregnation. The resulting composite shows enhanced photocatalytic activity for hydrogen evolution compared to pristine CNx under monochromatic visible light (λ = 420 nm) irradiation in the presence of sacrificial reducing agents. The light-driven dynamics of excitons and charges involved in hydrogen evolution catalysis were studied by a combination of spectroscopic (steady-state and time-resolved photoluminescence, femtosecond time-resolved transient absorption) and photoelectrochemical (open-circuit photopotential transients) methods. We demonstrate that the molecular molybdenum sulfide catalyst, at optimum loading (10 wt% nominal), improves the charge separation in the CNx absorber by facilitating the depopulation of emissive (band-edge) or non-emissive (shallow trap) states, followed by an effectively catalyzed transfer of electrons from the charge-separated state (deep trap) to protons in the solution. The results provide important insights into the complex interplay between polymeric light absorbers and molecular redox catalysts, indicating that the electron transfer to the catalyst occurs on relatively longer (nanosecond to seconds) time scale, as the catalyst had no impact on the ultrafast (sub-nanosecond) photoinduced kinetics in the CNx. These findings are of crucial importance for further development of soft-matter based architectures for solar fuels production.

中文翻译:

聚合氮化碳与分子硫代钼酸盐催化剂的耦合:光驱氢释放中的激子和电荷动力学

从水中释放出太阳能氢是克服不断增长的能源需求和相关环境问题的必要步骤。基于聚合物光吸收剂和高效分子催化剂的低成本光催化体系结构可能是解决此问题的有吸引力的平台。但是,迄今为止,我们对这些系统的机械知识仍很不完善。在这项研究中,通过浸渍将分子硫化钼放氢催化剂[Mo 3 S 13 ] 2−负载到聚合物氮化碳(CN x)光吸收剂上。与原始CN x相比,所得复合材料显示出更高的光催化活性,促进了氢的释放。在牺牲还原剂的存在下,在单色可见光(λ = 420 nm)照射下。结合光谱学(稳态和时间分辨光致发光,飞秒时间分辨瞬态吸收)和光电化学(开路光势瞬变)方法,研究了参与氢释放催化的激子和电荷的光动力学。我们证明了分子硫化钼催化剂在最佳负载量(标称重量为10 wt%)下可改善CN x中的电荷分离通过促进发射态(带状边缘)或非发射态(浅陷阱)的消失,然后有效催化电子从电荷分离态(深陷阱)转移到溶液中的质子,从而形成吸收体。结果为聚合物光吸收剂和分子氧化还原催化剂之间复杂的相互作用提供了重要的见解,表明电子转移到催化剂的时间相对较长(纳秒至秒),因为催化剂对超快(亚微米级)没有影响。纳秒)在CN光敏反应动力学X。这些发现对于进一步开发基于软物质的太阳能燃料生产体系至关重要。
更新日期:2020-11-03
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