AA- and ABA-stacked carbon nitride (C3N4): novel photocatalytic water splitting solar-to-hydrogen energy conversion

Abstract

We report the development of the C₃N₄ structure by integrating two different structures: (i) two identical layers as AA-stacked C₃N₄ and (ii) intercalating one different layer between two identical layers as ABA-stacked C₃N₄. This in turn endows C₃N₄ with significantly promoted charge migration, up-shifted conduction-band (CB) level, enhanced CB potential from −0.89 eV (AA-stacked C₃N₄) to −1.03 eV (ABA-stacked C₃N₄), broadened band gap as well as enhanced surface area, all of which favor the enhancement of the photocatalytic performance. The optical absorption level exhibited significant enhancement in the visible light region when shifting from AA-stacked C₃N₄ to ABA-stacked C₃N₄, where the absorption edge moves from λ = 508.1 → λ = 454.1 nm. This corresponds to the direct optical band gap of 2.44 eV → 2.73 eV, which is well matched with the solar spectrum and the sufficient negative CB potential for H⁺/H₂ reduction. Based on these results, we can conclude that AA-stacked and ABA-stacked C₃N₄ satisfies all the requirements to be efficient photocatalysts. This study will significantly improve the search efficiency and considerably aid the experimentalists in the exploration of novel photocatalysts.