A strategy of enhancing photoactivity of TiO2 via facet-dependent pyrolysis of dicyandiamide

A deep understanding of the relationship between surface chemistry and activity enhancement of photocatalysts at the molecular level is still lacking despite the increasing interest in this exciting field. In this paper, the influence of exposed facets on the pyrolysis of organic modifiers and thereafter the photoactivity of photo catalysts was investigated by using the thermal pyrolysis of dicyanodiamide (DCDA) over TiO2 as an example. Experimental results revealed that {001} -faceted TiO2 was favorable for the formation of carbon dots modified TiO2 nanosheets. In contrast, the deep pyrolysis of organic precursor over {101} facets contributed to the formation of oxygen-deficient TiO2. Benefitted from the oxygen vacancy mediated mechanism, nearly order-of-magnitude improvement in hydrogen evolution rate was achieved for 101 -faceted TiO2 treated by DCDA, which was much higher than the treated 001-TiO2 and P25. This work not only provides new insights into the facet-dependent activity of TiO2 photocatalysts, but also offers a facile strategy for exploring high-efficiency photocatalysts for water splitting through facet tailoring.