[Paper Review] Bilayer C2N Nanosheet: A Promising Metal-free Photocatalyst for Water Splitting

Ruiqi Zhang, Jinlong Yang|arXiv (Cornell University)|May 11, 2015

Graphene research and applicationsMaterials Science1 citations

TL;DR

This study proposes few-layer C2N nanosheets as a metal-free, visible-light-driven photocatalyst for water splitting. Using density functional theory, it demonstrates that bilayer and multilayer C2N exhibit tunable direct bandgaps (1.84–2.47 eV), favorable band edge positions, and strong visible-light absorption, making them promising for sustainable hydrogen production without noble metals.

ABSTRACT

Successful synthesis of the nitrogenated holey two-dimensional structures C2N (Nat. Commun. 2015, 6, 6486) using simply wet-chemical reaction offer a cost-effective way to generate other 2D materials with novel optical and electronic properties. On basis of the density functional theory calculations, we investigate electronic properties of monolayer and multilayer C2N. We find that few-layer C2N have a direct bandgap and the direct bandgap of the system can vary from 2.47 eV for monolayer to 1.84 eV for a five-layer. Besides, for the few-layer C2N, appropriate band gap, band edge alignments, and strong visible-light absorption demonstrate it may be a potential metal-free visible-light driven photocatalyst for water splitting.

Motivation & Objective

• To explore the electronic and optical properties of few-layer C2N nanosheets for photocatalytic applications.
• To evaluate the potential of C2N as a metal-free alternative to conventional photocatalysts in water splitting.
• To determine if bandgap tuning and favorable band edge alignment in C2N enable efficient visible-light-driven hydrogen production.
• To assess the role of layer number in modulating electronic structure and photocatalytic activity.

Proposed method

• Density functional theory (DFT) calculations were used to investigate the electronic structure of monolayer and multilayer C2N.
• The bandgap and band edge positions of few-layer C2N were computed as a function of layer count.
• Optical absorption spectra were calculated to evaluate visible-light response across different layer thicknesses.
• The stability and electronic properties of C2N were analyzed to confirm feasibility for photocatalytic applications.
• Band alignment with respect to water redox potentials was evaluated to determine thermodynamic feasibility of water splitting.

Experimental results

Research questions

• RQ1 Can few-layer C2N nanosheets exhibit a direct bandgap suitable for visible-light absorption?
• RQ2 How does the bandgap of C2N vary with increasing layer count?
• RQ3 Are the conduction and valence band edges of C2N positioned favorably for water reduction and oxidation?
• RQ4 Does C2N show strong absorption in the visible light range, enabling efficient photocatalytic activity?

Key findings

• Few-layer C2N exhibits a direct bandgap that decreases from 2.47 eV in monolayer to 1.84 eV in five-layer structures.
• The band edge positions of few-layer C2N are thermodynamically favorable for both water reduction and oxidation under visible light.
• C2N demonstrates strong visible-light absorption, indicating high potential for light harvesting in photocatalytic applications.
• The system maintains a direct bandgap across all studied layer thicknesses, which enhances radiative recombination efficiency.
• The electronic structure of C2N supports efficient charge separation and transfer, critical for photocatalytic water splitting.