High‐efficiency composite photocatalyst of NaYF₄:Yb,Er/BiOBr with visible‐near‐infrared light response

Photocatalysis presents a promising solution for environmental remediation, though conventional photocatalysts remain constrained to the ultraviolet and partially visible regions of the solar spectrum. To address this limitation, we developed a NaYF 4 :Yb,Er/BiOBr (N/B) composite photocatalyst, leveraging upconversion luminescence to convert near‐infrared photons into visible light while utilizing BiOBr's narrow bandgap for enhanced visible‐light absorption. The composite photocatalyst was fabricated via a two‐step solvothermal approach and evaluated for the degradation of methyl orange (MO). Remarkably, the N/B‐120°C sample demonstrated superior photocatalytic activity, achieving degradation rates 2.4‐ and 5.4‐fold higher than those of pristine BiOBr and commercial TiO 2 (P25), respectively. This enhanced performance is attributed to synergistic effects including an increased specific surface area (23.96 m 2 /g for N/B‐120°C vs. 16.28 m 2 /g for BiOBr), reduced charge transfer resistance (as evidenced by electrochemical impedance spectroscopy (EIS) Nyquist plots), elevated oxygen vacancy concentration (as verified by x‐ray photoelectron spectroscopy [XPS]), and extended solar spectral utilization range (400–980 nm). This work presents a viable strategy to improve the efficiency of photocatalysis.