Upconversion boosting pollutants degradation efficiency in wide-spectrum responsive photocatalysts

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 CoWO 4 @NaYF 4 :Yb 3+ ,Er 3+ were designed and developed herein. The structural characterization, morphology and elemental composition analysis demonstrated that heterojunctions between CoWO 4 and NaYF 4 :Yb 3+ ,Er 3+ were indeed formed in the composite photocatalysts. Moreover, CoWO 4 @NaYF 4 :Yb 3+ ,Er 3+ heterojunction photocatalysts exhibited higher pollutants degradation efficiency. Especially, a great enhancement of +87% on the photocatalytic activity was achieved in the heterojunction photocatalyst of 60CoWO 4 –NaYF 4 :Yb 3+ ,Er 3+ compared with pure CoWO 4 . 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 CoWO 4 . Eventually, an underlying mechanism was proposed that the enhanced photocatalytic activity should be attributed to the wide-spectrum responsive features of CoWO 4 @NaYF 4 :Yb 3+ ,Er 3+ heterojunction photocatalysts. Within the heterostructures, CoWO 4 photocatalyst can absorb both the UV–Vis light due to its narrow bandgap and the Near-Infrared energy through the upconversion NaYF 4 :Yb 3+ ,Er 3+ , thereby utilizing solar energy more efficiently in a wide-spectrum range for photocatalytic reactions.