摘要
将负载Pt的TiO2与Ru(Ⅱ)三亚胺敏化剂(RuP)相结合,构建了一种染料敏化光催化剂RuP/Pt/TiO2,并探索其在光化学析氢反应中的应用.通过对比实验,评估了该催化剂与Pt插层HCa2Nb3O10纳米片催化剂RuP/Pt/HCa2Nb3O10在不同电子供体条件下的析氢活性.当以乙二胺四乙酸(EDTA)二钠盐二水合物作为牺牲供体时,RuP/Pt/TiO2表现出比RuP/Pt/HCa2Nb3O10更高的催化活性,这归因于Pt/TiO2复合材料在牺牲性还原剂EDTA存在下,能够有效抑制反向电子传递,从而提高了光生电子的利用效率.然而,当采用NaI作为电子供体时,由于RuP/Pt/TiO2存在向I-氧化产生的电子受体I3-的反向电子传递,导致其活性显著降低.为了克服这一问题,通过用阴离子聚合物(如聚甲基丙烯酸钠PMA或聚苯乙烯磺酸钠PSS)对RuP/Pt/TiO2进行改性,这些聚合物能够有效抑制I3-对导带电子的捕获,进而提升了在NaI水溶液中的产氢活性.尽管如此,改性后的RuP/Pt/TiO2材料在产氢活性上仍未超过未改性的RuP/Pt/HCa2Nb3O10.瞬态吸收测量结果表明,与HCa2Nb3O10相比,TiO2的反向电子转移速率较慢,但电子向I3的转移反应却快得多.这一发现凸显了催化剂设计的复杂性及其对反应性能的重要影响.在设计光催化剂时,需要综合考虑半导体材料、染料敏化剂以及电子供体的相互作用,以实现高效的电子转移和抑制不必要的反向电子传递.综上可见,Pt/TiO2基染料敏化光催化剂在与牺牲还原剂(如EDTA)的反应中表现出色,其中可以忽略更易还原产物的反向电子转移反应;然而,当使用可逆电子供体(如NaI)时,则需要对催化剂进行针对性的设计,以达到理想的反应活性.此外,通过优化染料敏化析氢体系中的助催化剂,有望进一步提升正向电子传递效率,从而显著增强复合材料整体的光催化性能.本研究不仅深化了对光催化析氢机制的理解,也为未来高效光催化剂的设计提供了有益的参考.
Abstract
A dye-sensitized photocatalyst combining Pt-loaded TiOa and Ru(Ⅱ)tris-diimine sensitizer(RuP)was constructed and its activity for photochemical hydrogen evolution was compared with that of Pt-intercalated HCa2Nb3O10 nanosheets.When the sacrificial donor ethylenediaminetetraacetic acid(EDTA)disodium salt dihydrate was used,RuP/Pt/TiO2 showed higher activity than RuP/Pt/HCa2Nb3O10.In contrast,when NaI(a reversible electron donor)was used,RuP/Pt/TiO2 showed little activity due to back electron transfer to the electron acceptor(I2-),which was gener-ated as the oxidation product of I-.By modification with anionic polymers(sodium poly(styrenesulfonate)or sodium polymethacrylate)that could inhibit the scavenging of conduction band electrons by I3-,the H2 production activity from aqueous NaI was improved,but it did not exceed that of RuP/Pt/HCa2Nb3O10.Transient absorption measurements showed that the rate of semiconductor-to-dye back electron transfer was slower in the case of TiO2 than HCa2Nb3O10,but the electron transfer reaction to I2 was much faster.These results indicate that Pt/TiO2 is useful for reactions with sacrificial reductants(e.g.,EDTA),where the back electron transfer reaction to the more reducible product can be neglected.However,more careful design of the catalyst will be nec-essary when a reversible electron donor is employed.
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