High surface area TiO2 was synthetized by means of a solvothermal method and it was then used to prepare two photocatalysts based on copper-modified TiO2. Two different preparation approaches have been adopted based on the use of the same amount of Cu2O (0.5% w/w) as a reactant. The spectroscopic characterization shows that the two preparation procedures lead to distinct distributions of Cu2O and other Cu-based species in the final composite materials and that the photoactivity of the solids is strictly related to the nature of the copper species. The joint application of CW-EPR and optical spectroscopy, both employed in catalytic conditions as a sort of “operando” mode, allowed monitoring the evolution of the photocatalytic systems occurring during the H2 evolution reaction (HER). The effect of water coordination on the Cu(II) species at the surface of titania has been revealed by EPR. The successive photoreduction of the system in the early steps of the photocatalytic reaction involves the reduction of Cu2+, the formation of Ti3+ centres in the oxide matrix and that of metallic copper particles that partially inactivate the system.

中文翻译：

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析氢反应过程中铜-TiO2 体系表面铜物种的自组织：EPR 和光谱学的联合研究

通过溶剂热法合成了高表面积TiO2，然后将其用于制备两种基于铜改性TiO2的光催化剂。基于使用相同量的 Cu2O (0.5% w/w) 作为反应物，采用了两种不同的制备方法。光谱表征表明，两种制备程序导致最终复合材料中 Cu2O 和其他铜基物质的不同分布，并且固体的光活性与铜物质的性质密切相关。CW-EPR 和光谱学的联合应用，都在催化条件下用作一种“操作”模式，允许监测在 H2 演化反应 (HER) 期间发生的光催化系统的演化。EPR 揭示了水配位对二氧化钛表面 Cu(II) 物种的影响。在光催化反应的早期阶段，系统的连续光还原包括 Cu2+ 的还原、氧化物基质中 Ti3+ 中心的形成以及部分使系统失活的金属铜颗粒的形成。