Red Phosphorus/Carbon Nitride van der Waals Heterostructure for Photocatalytic Pure Water Splitting under Wide-Spectrum Light Irradiation

Abstract

Developing active photocatalysts using wide-spectrum light is crucial to promote the application of photocatalytic water splitting. Elemental red phosphorus (RP) has attracted much attention as a potential nonmetal photocatalyst owing to its low cost, earth abundance, and narrow bandgap. Herein, RP nanosheets were synthesized and tightly combined with carbon nitride (CN) framework nanosheets to form RP/CN van der Waals (vdW) heterostructure. CN nanosheets could act as a substrate to generate RP nanosheets through a “confinement effect”. This hybrid photocatalyst could utilize the incident light with the wavelength longer than 620 nm for pure water splitting, with hydrogen production activity of 367.0 μmol h–1g–1 under full arc illustration and 239.8 μmol h–1g–1 under visible light irradiation. The improved photocatalytic property was ascribed to the wide light absorption and intimate electronic coupling between 2D RP and 2D CN for accelerated charge transfer. Instead of O2, water was oxidized into H2O2 via a two-electron pathway, which could avoid the potential explosion by producing H2 and O2 simultaneously. This work proved the great potential of RP-based vdW heterostructures for solar-driven water splitting.

2D van der Waals Heterojunction Nanophotonic Devices: From Fabrication to Performance

“…Red phosphorus (RP)/carbon nitride (CN) vdWh were synthesized by Wang et al, and the CN nanosheets can be used as substrates to produce RP nanosheets through a "confinement effect" (see Figure 9e). [97] The composite photocatalyst could decompose pure water by incident light with a wavelength greater than 620 nm, and its hydrogen evolution rate was 367.0 µmol h −1 g −1 in the full arc diagram and 239.8 µmol h −1 g −1 for visible light. The improved of photocatalytic performance was attributed to the broad-spectrum absorption and tight electron interactions in a RP/CN vdWh, which accelerated CT. Table 1 summarizes the main experimental results of vdWhs for hydrogen production in recent years, including heterojunction structure, preparation method, light source, hydrogen production efficiency, and the corresponding years for comparison.…”

“…The improved of photocatalytic performance was attributed to the broad-spectrum absorption and tight electron interactions in a RP/CN vdWh, which accelerated CT. Table 1 summarizes the main experimental results of vdWhs for hydrogen production in recent years, including heterojunction structure, preparation method, light source, hydrogen production efficiency, and the corresponding years for comparison. [75,94,[96][97][98][99][100][101] In terms of photocatalytic CO 2 reduction, Li et al prepared atom thick CN/Bi 9 O 7.5 S 6 (BOS) vdWh for CO 2 photoreduction (see Figure 10a). [102] Experiments and theoretical calculations showed that CO* adsorbed stronger than CN, and could be hydrogenated before desorption, which explained why the main products of photocatalytic CO 2 reduction on BOS were CH 4 and CH 3 OH.…”

“…Reproduced with permission. [97] Copyright 2020, American Chemical Society. f) The progress of photocatalytic hydrogen evolution of a RP/CN vdWh.…”

“…Copyright 2020, Elsevier Ltd. e) AFM of RP/CN. Reproduced with permission [97]. Copyright 2020, American Chemical Society.…”

“…f) The progress of photocatalytic hydrogen evolution of a RP/CN vdWh. Reproduced with permission [97]. Copyright 2020, American Chemical Society.…”