Graphene-Based Nanocomposites for Efficient Photocatalytic Hydrogen Evolution: Insight into the Interface toward Separation of Photogenerated Charges

Although the reduced graphene oxide (rGO) has been intensively applied for photocatalytic H-2 evolution, no enough attention was given to study the interface between the photocatalyst and rGO, which is the key point to affect the transportation of the photogenerated electron. Herein, in order to research the heterojunction interface, a series of SrTiO3 photocatalysts with different crystal facets were fabricated to be loaded with the rGO for photocatalytic H-2 evolution. The characterizations and theory calculation verified that the rGO was mainly anchored on the Ti-O bond of the SrTiO3 in the composite. Therefore, compared to the {001} facets sample, the {110} facets of the SrTiO3, which exposed more Ti and O atoms, could form a stronger bond with the rGO. Additionally, the density functional theory study deduced that the photoinduced electron could immigrate rapidly from the Ti-O bond to the rGO in the composite, which was in good agreement with the results of photoelectrochemical and photoluminescence experiments. Meanwhile, experimentally, the 1% wt rGO@SrTiO3 with {110} facets nanocomposite showed the superior photocatalytic H-2 yield rate (3.82 mmol/h/g), which was 2.2 times and 3.2 times higher than that of the pure SrTiO3 with the same facets and 1% wt rGO@SrTiO3 with {001} facets, respectively. Both experiments and theoretical calculations unveiled that the synergetic effect of SrTiO3 facets engineering and the rGO loading effectively prompted the immigration of photoinduced electrons at the nanocomposite interface. This work provides a rational thinking of a high efficiency rGO-based heterogeneous photocatalysts for solar energy conversion.