Metallic Tungsten Carbide Coupled with Liquid-Phase Dye Photosensitizer for Efficient Photocatalytic Hydrogen Production

Abstract

Tungsten carbide (WC) is commonly used as a photocatalytic material for hydrogen production via water reduction. However, it is often combined with an effective photoabsorber to provide sufficient photoactivity. This is attributed to the narrow band gap of WC, which leads to an inadequate redox capability for water reduction. Notably, this limitation was overcome using a novel solid-liquid photocatalytic system that compliments bare WC photocatalysts with liquid-phase photosensitizing erythrosine B (ErB). The proposed concept eliminates the need to couple WC with photoabsorbing semiconductors, which often requires tedious procedures for the proper functionalization of photocatalytic composites. The experimental results indicated significant hydrogen production from the proposed solid-liquid photocatalytic system under irradiation with visible light (λ = 520 nm); however, only in the presence of triethanolamine (TEOA) as a sacrificial reagent. Evidently, a blank experiment with only WC and ErB under typical photoreaction conditions exhibited nearly zero photoactivity and the production of H2 was undetected. Similarly, nonactivity was observed for the photoreaction in the presence of ErB or WC in the irradiated TEOA solution. These blank experiments confirmed the significance of all three components, namely WC, ErB, and TEOA, which functioned as the photocatalyst, photoabsorber, and sacrificial reagent, respectively, for suitable H2 production in the proposed system. The effects of three critical parameters, such as pH, ErB concentration, and WC concentration, were systematically investigated. The optimum pH for H2 production was 8, with a slight variation to more basic or acidic conditions reducing the photoactivity of the system. At pH < 8, part of TEOA undergoes partial protonation, thereby losing its activity as a sacrificial reagent in the photocatalytic system. As the pH increased to > 8, the low proton concentration in the reaction medium perturbed the thermodynamic drive, leading to suppressed H2 production. The optimum ErB concentration was 1 mmol•L −1 , and decreasing or increasing the ErB concentration from the optimal point was detrimental to H2 production. The diluted system (ErB concentration < 1 mmol•L −1 ) provided insufficient sensitizing agents, whereas the concentrated system (> 1 mmol•L −1 ErB) induced significant scattering effects that prevent light from penetrating into the reactive liquid phase. Conversely, the WC concentration exhibited a positive correlation with H2

Design and Architecture of P-O Co-Doped Porous g-C3N4 by Supramolecular Self-Assembly for Enhanced Hydrogen Evolution

“…Currently, Erythrosin B(EB) sensitization has attracted much attention in H 2 evolution. Lei et al reported on a novel solid-liquid photocatalytic system that compliments tungsten carbide (WC) photocatalysts with liquid-phase photosensitizing EB; the hydrogen evolution rate reached 66 µmol/h, while pure WC showed poor activity (almost no H 2 generation) [44]. Zhang et al used EB as a sensitizer for Cu/g-C 3 N 4 photocatalytic hydrogen evolution and reached a rate that was 26 times higher than that of the non-sensitized system [45].…”

In situ photodeposition of loaded Co–MoSx for promoting visible-light g-C3N4 photocatalytic hydrogen production performance

“…1 In response to this, photocatalytic technology that realizes hydrogen production from water enables a one-stop solution to both energy crisis and environmental protection. [2][3][4][5][6] Signicantly, graphite phase carbon nitride (g-C 3 N 4 , abbreviated as CN) with a two-dimensional lamellar structure is widely investigated as a photocatalytic material due to its suitable band gap structure, good physical and chemical stability, and high availability. 7 One major drawback of such material is associated with its relatively large band gap (2.7 eV) for very limited solar utilization.…”