Nanoarchitectonics with W18O49 nanobelts and B-doped g-C3N4 nanosheets towards NO and 4-nitrophenol conversion

Abstract

Construction of heterostructures has been an effective approach for suppressing recombination of photogenerated charge carriers of graphitic carbon nitride (g-C₃N₄) materials and facilitating solar energy harvesting. In this paper, superior thin B-doped g-C₃N₄ nanosheets are synthesized via mechano-chemical pre-treatment and two-step thermal polymerization (at 600 and 700 °C) using boric acid and melamine as precursors. The in situ growth of W₁₈O₄₉ nanobelts on B-g-C₃N₄ nanosheets is attained via solvothermal synthesis. W₁₈O₄₉ nanobelts are horizontally implanted onto g-C₃N₄ nanosheets to construct a Z-scheme heterostructure with extended light absorption in the near infrared range. Well-developed interfaces between W₁₈O₄₉ and B-g-C₃N₄ are crucial for the enhanced transfer efficiency of photogenerated charge carriers. The W₁₈O₄₉/B-g-C₃N₄ samples fabricated using optimized conditions show excellent photocatalytic performance in NO and 4-nitrophenol oxidation conversion. The W₁₈O₄₉/B-g-C₃N₄ composites attain a NO removal efficiency of 64% (at an initial NO concentration of 600 ppb in air) with a low NO₂ selectivity (6.4%), which is more efficient than that of the commercial P25 (TiO₂, with a 40% NO removal rate). These are mainly attributed to the formed Z-scheme W₁₈O₄₉/B-g-C₃N₄ layered heterostructure, increased specific surface area and improved interfacial structure. The heterostructure construction, light absorption range extension, and adjustment on the band gap of the composite material are discussed in detail. Under full-spectrum irradiation conditions, the W₁₈O₄₉/B-g-C₃N₄ heterostructures also show excellent light-assisted 4-nitrophenol elimination (via selective hydrogenation to valuable 4-aminophenol) performance, attaining a 99% 4-nitrophenol reduction rate.