The roles of graphene and sandwich structure in rGO/BiOI/rGO to enhance the photoelectrocatalytic activity

A special rGO/BiOI/rGO sandwich structure was fabricated, which showed an excellent visible-light photoelectrocatalytic activity much higher than BiOI/rGO and BiOI. Photocatalytic activity depended on charge separation, charge injection and effective light absorption. The charge separation efficiency and the charge injection efficiency of rGO/BiOI/rGO were quantified to be much higher than that of BiOI/rGO and BiOI. So the remarkably enhanced photoelectrocatalytic performance was attributed to the significant enhancement in charge separation and charge injection resulted from more electron transfer channels due to the upper layer and underlayer rGO in the sandwich structure. However, the effective light absorption was not improved since the light absorption efficiency of rGO/BiOI/rGO was almost the same as that of BiOI and BiOI/rGO, although the incorporation of rGO broadened the light absorption range and enhanced the light absorption intensity. This work provided a deep insight for the construction of novel rGO-based photocatalysts with hierarchical nano-architectures exhibiting excellent photoelectrocatalytic performances.