Utilizing Upconversion Emission to Improve the Photocatalytic Performance of the BiOI Microplate: A Bifunctional Platform for Pollutant Degradation and Hydrogen Production

Developing novel photocatalysts with intense sunlight-harvesting capacity is still a challenge to realize pollutant degradation and water splitting. To settle this issue, we couple the Gd2MoO6:0.04Er3+/0.10Yb3+ (GMEY) upconverting particle with the BiOI microplate to construct the BiOI@GMEY-x composites. Their corresponding crystal structure, morphology, chemical composition, and upconversion (UC) properties are studied. Due to the UC emission behavior of the GMEY particle, near-infrared (NIR) light can be converted to green and red emissions which could be reabsorbed by the BiOI microplate, bringing about the full use of visible–NIR light by the prepared composites for photocatalysis. Upon visible light irradiation, the resultant samples exhibit good photocatalytic activities in the degradation of methyl blue, RhB, and methyl orange. Compared with that of the BiOI microplate, improved photocatalytic activity is achieved in the resultant composites due to the effect of a built-in electric field and an enhanced sunlight-harvesting ability. Furthermore, the h+ and •O2– species are responsible for the mechanism of photocatalysis. Additionally, excited by full spectrum light, the H2 production capacity of the designed samples is also investigated. It is found that the BiOI@GMEY-10 composite can split water efficiently and its H2 production rate is 10.35 μmol/g/h. These results indicate that both pollutant degradation and water splitting are able to be realized by utilizing the BiOI@GMEY-x composites.