Abstract: With regarding to the solar energy conversion applications, BiOBr demonstrated superior photocatalytic property, while its photothermal property and application need further investigation and exploitation. Firstly, BiOBr nanosheets were prepared by hydrothermal method, and then the BiOBr nanopowders were chemically reduced by sodium borohydride. The characterization results show that, with the concentration of sodium borohydride increased, the dense BiOBr nanosheets initially transform into BiOBr/Bi composite porous nanosheets, and then metallic Bi porous nanosheets. The formation of metallic Bi and porous structure is benefit for improving the light absorption ability and specific surface area. The BiOBr/Bi composite porous nanosheets, which are obtained by reduction using 20 g·L⁻¹ NaBH₄ solution, possess the best light absorption ability and specific surface area, and the wetting property is also excellent. It therefore demonstrate the best interfacial photothermal driven water evaporation performance. The water evaporation rate reach to 2.18 kg·m⁻²·h⁻¹, which is twice that of BiOBr nanosheets.