Metal-Free Doping Strategies in Two-Dimensional Carbon Nitride C₄N₂ for Enhanced Hydrogen Evolution Catalysis

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• The hydrogen evolution reaction (HER) is crucial for sustainable energy. Carbon-nitrogen (C4N2) nanosheets are explored as potential catalysts.
• Pristine C36N18 nanosheets show limited HER activity due to high positive Gibbs free energies for hydrogen adsorption.

Purpose of the Study:

• To investigate the structural, electronic, and catalytic properties of pristine and doped C4N2 nanosheets for HER.
• To enhance HER catalytic performance by doping C36N18 nanosheets with B, Si, or P at nitrogen sites.

Main Methods:

• Density Functional Theory (DFT) calculations were used to study structural and electronic properties.
• Analysis of Gibbs free energies, band structure, projected density of states (PDOS), charge density, and Bader charges.
• Evaluation of catalytic performance for the hydrogen evolution reaction (HER).

Main Results:

• Pristine C36N18 nanosheets exhibit poor HER activity (Gibbs free energy > 2.2 eV).
• Boron-doped C36N17 nanosheets demonstrate significantly enhanced HER activity with a near-zero Gibbs free energy (≈-0.2 eV), indicating efficient hydrogen adsorption.
• Doping, especially with Boron, substantially modifies the electronic structure, optimizing hydrogen adsorption and facilitating the HER.

Conclusions:

• Boron-doped C36N17 nanosheets are promising candidates for efficient HER catalysis.
• Electronic structure modifications through doping are key to optimizing catalytic performance.
• Stacking configurations have a minor impact compared to the significant effect of doping.