Noble-metal and cocatalyst free W2N/C/TiO photocatalysts for efficient photocatalytic overall water splitting in visible and near-infrared light regions

Abstract

Photocatalysts that can not only harvest broader solar irradiation (from UV to near infrared (NIR) light region) but also achieve higher solar-to-hydrogen conversion efficiency are critical for solar hydrogen economy. In this research, we report a ternary bridge chain W2N/C/TiO photocatalyst for the first time to realize an efficient and stable visible and NIR light driven water splitting. This photocatalyst can realize overall water splitting using bifunctional mechanism with hydrogen (H2) generation part and oxygen (O2) generation part. The optimal H2 and O2 generation rates based on the W2N/C/TiO photocatalyst are 2.01 and 1.11 μmol g-1h−1 under the irradiation of NIR light (λ > 700 nm). In this new photocatalyst, W2N and TiO were integrated into nanosized carbon fibers that serve as H2 and O2 evolution active sites. And the hydrogen apparent quantum efficiency (AQE) for W2N/C/TiO composite photocatalyst for NIR light water splitting can reach as high as 2.14% at 700 ± 15 nm. This research indicates that W2N/C/TiO photocatalyst can be effective under broaden (Ultraviolet, Visible and Near-Infrared) light. Combining interfacial and electrochemical characterizations, we have found that W2N/C/TiO photocatalyst can efficiently separate charges through the interfaces between C/W2N and C/TiO and harvest low energy photons in NIR region. Because of the bridge chain structure among W2N, C, and TiO electron transfer from W2N to TiO via C can promote charge separation and impede the recombination of photo-generated electron and hole pairs. It is therefore that this bridge chain structured W2N/C/TiO nanofiber photocatalyst can be a promising material for overall water splitting due to the capacity to utilize a broader solar spectrum.