Selective Photocatalytic Reduction of 3‐Nitrophenol to 3‐Aminophenol by Anatase and Rutile TiO₂ – What Stands Behind the Photoactivity?

Abstract

The photocatalytic selective reduction of 3‐nitrophenol to 3‐aminophenol was studied in the presence of titanium dioxide in the form of various anatase and rutile compositions. The reaction progress is altered by various parameters, which can be classified as intrinsic (depending on the chemical, structural, and electronic features) and extrinsic (depending on the reaction and conditions). The goal of the studies was to understand the influence of intrinsic factors and to compare the performance of anatase and rutile materials. The (photo)electrochemical analysis revealed unequivocally the differences in interfacial electron transfer, charge recombination, reduction driving force, and methanol photooxidation efficiency for titania polymorphs. It appeared that all mentioned processes were phase‐dependent, and they contributed unequally to overall photocatalytic activity. In particular, methanol oxidation was the most efficient at the rutile phase, which overcame the critical limitation of the oxidation pathway and facilitated the reduction of 3‐nitrophenol. On the other hand, the dark electron transfer efficiency was highest at the anatase phase, despite the lower driving force in this case. The presented thorough and systematic analysis of the discussed photocatalytic system (the photocatalyst and the reaction) should allow the rational design of efficient and selective photocatalysts.