article · The Journal of Physical Chemistry C
Computational modelling using first-principles density functional theory examined the electronic, optical, and photocatalytic properties of a two-dimensional heterostructure combining bilayer graphitic carbon nitride and bilayer hexagonal boron nitride. The stacked material demonstrates thermodynamic stability supported by weak van der Waals interactions. Combining these layers reduces the overall band gap and shifts optical absorption towards the visible-light spectrum. When illuminated, the interface creates an internal electric field driven by work-function differences, establishing a type-II pathway that separates electrical charges by concentrating electrons on the boron nitride layer and holes on the carbon nitride layer. Thermodynamic calculations show favourable conditions for hydrogen adsorption in weakly acidic environments, alongside potential for oxygen evolution under sufficient hole chemical potential. These findings highlight the heterostructure as a viable metal-free candidate for solar-driven water splitting.
Solar-driven water splitting offers a pathway to produce clean hydrogen fuel without relying on scarce or toxic metal catalysts. By demonstrating how combining two distinct non-metallic layers improves visible-light absorption and charge separation, this work provides fundamental insights into designing efficient, metal-free catalysts for renewable energy conversion.
This study represents early-stage research based entirely on theoretical calculations. If realised physically, the design could inform developers of green hydrogen systems and catalyst manufacturers seeking metal-free alternatives for solar water splitting. However, the technology remains far from commercial use, requiring experimental synthesis, stability testing, and efficiency validation in operational environments before any commercial pathway can be established.
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Abstract Two-dimensional van der Waals heterostructures provide a promising platform for improving charge separation and tuning the optical and electronic properties of metal-free photocatalysts. In this work, first-principles density functional theory (DFT) calculations were employed to investigate the structural, electronic, optical, and photocatalytic properties of bilayer g-C3N4 ((2L) g-C3N4), bilayer h-BN ((2L) h-BN), and their vertically stacked bilayer g-C3N4/bilayer h-BN ((2L) g-C3N4/(2L) h-BN) heterostructure. The optimized heterostructure is found to be energetically and thermally stable, with interlayer interaction characteristic of weak van der Waals coupling. Hybrid-functional calculations reveal a reduced band gap relative to the isolated bilayers and an optical absorption edge shifted toward lower photon energies, extending closer to the visible-light region. Vacuum-level band alignment shows that (2L) g-C3N4 provides a photoresponsive framework but insufficient oxidation power for overall water splitting, whereas (2L) h-BN exhibits favorable redox-band positions despite its weak visible-range optical response. After contact, work-function mismatch drives electron transfer from h-BN to g-C3N4, inducing band bending and a built-in electric field at the interface. Under illumination, the heterostructure follows a type-II charge-separation pathway, in which electrons accumulate on the h-BN side while holes remain on the g-C3N4 side. Gibbs free-energy (ΔG) analysis indicates near-thermoneutral hydrogen adsorption under weakly acidic conditions, whereas the oxygen evolution reaction becomes thermodynamically feasible only under sufficiently high hole chemical potential, highlighting the intrinsic catalytic capability of the heterostructure. These results demonstrate that bilayer interface engineering effectively enhances charge separation and identify the (2L) g-C3N4/(2L) h-BN heterostructure as a promising metal-free platform for photocatalytic water splitting.
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DOI: 10.1021/acs.jpcc.6c02658
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