WN Coupled with Bi Nanoparticles to Enhance the Localized Surface Plasmon Resonance Effect for Photocatalytic Hydrogen Evolution

Conversion of light energy and chemical energy in a wide spectrum region, especially in the near-infrared (NIR) light region, is still a challenge in the field of photocatalysis. In this work, a layered Bi-WN photocatalyst with a heterojunction was prepared by reducing flake-shaped WN and flower-shaped Bi2O3 in an ammonia atmosphere. Under the process of NIR light (λ > 700 nm)-driven water splitting, the optimal hydrogen (H2) generation rates based on the Bi-WN photocatalyst can reach to 7.49 μmol g–1 h–1, which is 2.47 times higher than that of WN of 3.03 μmol g–1 h–1. The result indicates that the Bi-WN photocatalyst can be effective under NIR light. Through ultraviolet–visible–NIR diffuse reflectance spectrum analysis, it can be seen that the light absorption edge of Bi-WN is obviously redshifted. Combining the results of electrochemical characterizations, we have found that the addition of the Bi metal plays an important role in NIR light-driven water splitting. Under irradiation of NIR light, the electrons on the Bi-WN substrate are stronger due to local surface plasmon resonance, which reduces the possibility of recombination of photogenerated electrons and holes on WN. In addition, after the Bi metal absorbs the photon energy, the electron–hole pairs are separated, and the H2 production rate increases significantly under the combined action of the charge transfer mechanism and the local electric field enhancement mechanism.