Facet-dependent photocatalytic reduction of nitroaromatics using tailored SrTiO3 crystals: mechanism and reactivity enhancement†

This work presents a selective photocatalytic reduction of nitroaromatics to amines on tailored SrTiO₃ crystals. Exploring the role of exposed facets reveals their substantial impact on both the efficiency and selectivity of this type of reduction reaction. A series of uniform SrTiO₃ crystals with systematically varied morphologies, differing only in shape and type of exposed facets, were synthesised. Photoelectrochemical measurements and photodeposition experiments demonstrated that reduction reactions preferentially occur on the {001} facets, while oxidation predominantly takes place on the {110} facets. Furthermore, the {110} facets play a key role in enhancing charge separation, thereby significantly boosting photocatalytic activity. The changes in the efficiency of photocatalytic oxidation of terephthalic acid follow the same pattern as photocurrent generation. Using tailored SrTiO₃ crystals, the reduction of nitroaromatic compounds was achieved with outstanding conversion rates (up to 40 times higher compared to commercial SrTiO₃). Although {110} facets facilitate charge separation, transforming nitroaromatics to amines requires {001} planes.