Upconversion boosting pollutants degradation efficiency in wide-spectrum responsive photocatalysts.

ABSTRACT

Recently, the composite photocatalysts coupled with upconversion materials have received widespread attention due to higher utilization efficiency of solar energy in a wide-spectrum range. Novel heterojunction photocatalysts of CoWO4@NaYF4Yb3+,Er3+ were designed and developed herein. The structural characterization, morphology and elemental composition analysis demonstrated that heterojunctions between CoWO4 and NaYF4Yb3+,Er3+ were indeed formed in the composite photocatalysts. Moreover, CoWO4@NaYF4Yb3+,Er3+ heterojunction photocatalysts exhibited higher pollutants degradation efficiency. Especially, a great enhancement of +87% on the photocatalytic activity was achieved in the heterojunction photocatalyst of 60CoWO4-NaYF4Yb3+,Er3+ compared with pure CoWO4. The dominant radicals generated from the heterojunction photocatalysts were confirmed as the photo-generated holes (h+) and hydroxyl radicals (⋅OH) through the radical species trapping experiments and fluorescence detection, which is fully in line with the expected band structure characteristics of CoWO4. Eventually, an underlying mechanism was proposed that the enhanced photocatalytic activity should be attributed to the wide-spectrum responsive features of CoWO4@NaYF4Yb3+,Er3+ heterojunction photocatalysts. Within the heterostructures, CoWO4 photocatalyst can absorb both the UV-Vis light due to its narrow bandgap and the Near-Infrared energy through the upconversion NaYF4Yb3+,Er3+, thereby utilizing solar energy more efficiently in a wide-spectrum range for photocatalytic reactions.