Opposite effect of the Cu photodeposition on the ∙OH generation and diclofenac degradation depends on the exposed anatase facet

• Cu was photodeposited on the {0 0 1} and {1 0 1} TiO 2 facets with different loadings. • Degradation pathway of diclofenac depends on the light spectrum and TiO 2 presence. • Selective hydroxylation of diclofenac was achieved over the {0 0 1} facets. • Cu has an opposite effect on degradation and ∙OH generation, depending on the facet. • {0 0 1}/Cu X O has the highest activity due to the efficient charge utilization within the Z-scheme heterojunction. Exposition of a specific crystal facets and modification with co-catalysts are often used in order to improve photocatalytic activity of a material. However, considering complexity of these interactions, it is still challenging to fully understand and predict activity of a specific system. Here, we report combination of the {0 0 1} and {1 0 1} crystal facets of anatase TiO 2 with Cu X O co-catalyst, applied for diclofenac degradation, ∙OH generation and 4-nitrophenol reduction. Interestingly, we observed opposite effect of Cu for ∙OH generation and DCF degradation, with clear enhancement of the activity observed only for the {0 0 1} facets. EPR measurements further proved that for the most active material in this series, Cu exist as an atomically-scattered Cu 2+ species at the surface, achieved as the result of high surface development and high adsorption energy (from DFT). Based on the absorbance measurements and XPS analysis, these species are shown to be further reduced to Cu 2 O during degradation process. Compared to this, all other systems ({1 0 1} and all results for nitrophenol) showed reduction of the activity due to the Cu X O presence. In this regard, Cu X O cannot be seen as an universal reduction co-catalyst for TiO 2 , with final effect being clearly dependent on exposed facet and reaction. This is despite TiO 2 /Cu X O was found to form analogical, well-known Z-scheme junction in case of both surfaces. Ultimately, we showed that specifically {0 0 1} with Cu X O make highly synergistic combination for ROS generation.