Metal-free graphitic carbon nitride as mechano-catalyst for hydrogen evolution reaction

• The ΔGH∗0 on g-C3N4 is very sensitive to mechanical strain, leading to substantial tuning of the HER performance of g-C3N4.
• Mechanical strain can be introduced in g-C3N4 by doping a bridge carbon in g-C3N4 with an silicon to enhance the HER performance.
• Dynamic strain can promote the HER on g-C3N4, where part of the mechanical energy converted into chemical reaction energy, making g-C3N4 an excellent mechano-catalyst.

Graphitic carbon nitride (g-C3N4), as a promising metal-free catalyst for photo-catalytic and electrochemical water splitting, has recently attracted tremendous research interest. However, the underlying catalytic mechanism for the hydrogen evolution reaction (HER) is not fully understood. By using density functional theory calculations, here we have established that the binding free energy of hydrogen atom (ΔGH∗0) on g-C3N4 is very sensitive to mechanical strain, leading to substantial tuning of the HER performance of g-C3N4 at different coverages. The experimentally-observed high HER activity in N-doped graphene supported g-C3N4 (Zheng et al., 2014) is actually attributed to electron-transfer induced strain. A more practical strategy to induce mechanical strain in g-C3N4 is also proposed by doping a bridge carbon atom in g-C3N4 with an isoelectronic silicon atom. The calculated ΔGH∗0 on the Si-doped g-C3N4 is ideal for HER. Our results indicate that g-C3N4 would be an excellent metal-free mechano-catalyst for HER and this finding is expected to guide future experiments to efficiently split water into hydrogen based on the g-C3N4 materials.

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