Noble-metal and cocatalyst free W2N/C/TiO photocatalysts for efficient photocatalytic overall water splitting in visible and near-infrared light regions
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 W 2 N/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 (H 2 ) generation part and oxygen (O 2 ) generation part. The optimal H 2 and O 2 generation rates based on the W 2 N/C/TiO photocatalyst are 2.01 and 1.11 μmol g -1 h −1 under the irradiation of NIR light (λ > 700 nm). In this new photocatalyst, W 2 N and TiO were integrated into nanosized carbon fibers that serve as H 2 and O 2 evolution active sites. And the hydrogen apparent quantum efficiency (AQE) for W 2 N/C/TiO composite photocatalyst for NIR light water splitting can reach as high as 2.14% at 700 ± 15 nm. This research indicates that W 2 N/C/TiO photocatalyst can be effective under broaden (Ultraviolet, Visible and Near-Infrared) light. Combining interfacial and electrochemical characterizations, we have found that W 2 N/C/TiO photocatalyst can efficiently separate charges through the interfaces between C/W 2 N and C/TiO and harvest low energy photons in NIR region. Because of the bridge chain structure among W 2 N, C, and TiO electron transfer from W 2 N 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 W 2 N/C/TiO nanofiber photocatalyst can be a promising material for overall water splitting due to the capacity to utilize a broader solar spectrum.
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