One stone, three birds: up-conversion, photothermal and p-n heterojunction to boost BiOBr:Yb³⁺,Er³⁺/Cu₃Mo₂O₉ full spectrum photodegradation

Broadening spectral response range to realize the full spectrum photocatalysis is crucial to develop photocatalysts with satisfactory light-energy conversion ability. A full-spectrum driven p-n heterojunction photocatalytic system was rationally designed through introducing the Er³⁺/Yb³⁺ co-doped BiOBr with up-conversion effect as the collector of near infrared light and photocatalysts substrate. Meanwhile, Cu₃Mo₂O₉ with the photothermal effect as a heat source to accelerate the reaction at the surface through absorbing the near infrared light. The photocatalytic activity of BiOBr:Yb³⁺,Er³⁺/Cu₃Mo₂O₉ composite was markedly strengthened under visible and near infrared light irradiation, and the BiOBr:Yb³⁺,Er³⁺/Cu₃Mo₂O₉-5 composite displayed the optimal photodegradation activities for 0.03372 min⁻¹ and 0.058 h⁻¹, being 2.3-folds and 2.4-folds than that of pure BiOBr:Yb³⁺,Er³⁺ under the visible and near infrared light, respectively. The position of doped ions (Yb³⁺ and Er³⁺) in BiOBr:Yb³⁺,Er³⁺ was determined from the X-ray absorption fine structure spectra. And the reasonable mechanism of p-n heterojunction was proposed base on the results of experimental and density functional theory calculation. This work provides a rational strategy for the design and development of full-spectrum heterojunction photocatalysts with the up-conversion and photothermal effects to increase the photocatalytic performance.