Highly Ordered C-Rich Carbon Nitride Nanomaterials with Pyrrole and Imidazole Moieties for Photocatalytic Overall Water Splitting through Built-In Electric Field

The properties of carbon nitride nanomaterials are determined by their crystal structure, porosity, and C/N ratios, which in turn affect their applications. Recent research has shown that mesoporous N-rich nanomaterials containing five-membered heterocyclic rings exhibit significant activity in photocatalysis. However, the corresponding C-rich structures have not been reported. For this end, two stable C-rich buckled carbon nitride nanomaterials based on pyrrole and imidazole frameworks, namely C7N6 and C6N6, were predicted using first-principle computations. Both C7N6 and C6N6 exhibit reduced band gaps and broad optical absorptions in the visible region compared to those of the planar gh-C3N4. Moreover, due to the broken symmetry, the generated built-in electric field not only overcomes the restriction of the band structures in water splitting through band alignments but also accelerates the effective spatial separation of photocarriers. We explored the mechanisms of oxygen evolution (OER) and hydrogen evolution (HER) on their multilayers by the Gibb's free energy calculations, concluding that the designed C7N6 and C6N6 are potential photocatalysts for overall water splitting.