Promoting the spatial charge separation by building porous ZrO₂@TiO₂ heterostructure toward photocatalytic hydrogen...

The robust photocatalytic hydrogen evolution (PHE) from water needs an effective photogenerated charge spatial separation and enough contact between reactant and catalyst, but the synthesis of catalysts with the characteristics remains a challenge. Herein, we report the design of core-shell heterostructure consisted of thin TiO₂ layer uniformly coated on porous ZrO₂ polyhedron for effective PHE. In this system, UiO-66-NH₂, one of popular MOF with Zr as metal node, has been chosen as the precursor template due to its plentiful pores, uniform morphology, as well as the rich NH₂ groups. Our results show that Ti precursor can uniformly coat on UiO-66-NH₂, by means of interaction of tetrabutyl titanate (TBT) with -NH₃ in UiO-66-NH₂. Followed by the calcination, the Ti precursor and UiO-66-NH₂ can be converted into ZrO₂ and TiO₂, respectively, thus leading to the formation of ZrO₂@TiO₂ core-shell heterostructure. The ZrO₂@TiO₂-500 has the high specific surface area of 52.4 m² g^-1. Besides, the intimate contact of TiO₂ shell with ZrO₂ core facilitates the separation and migration of photoinduced carriers, exposing more active sites for the surface photocatalytic hydrogen evolution reaction. The spectrum and electrochemical characterization further exhibit the extended life of photon-generated carrier and easy mass transfer. The optimized ZrO₂@TiO₂-500 shows enhanced photocatalytic rate of 39.7 mmol h^-1 g^-1, much higher than those of ZrO₂ (0.8 mmol h^-1 g^-1) and TiO₂ (7.6 mmol h^-1 g^-1).