Electron spin-polarization and band gap engineering in carbon-modified graphitic carbon nitrides

Abstract

Graphitic carbon nitrides are attracting increasing interest in many fields such as fuel cells, photocatalytic decomposition of water and spintronic devices. Tailoring electronic band gaps and inducing electron spin-polarization are the keys of these applications. Using first-principles calculations, we demonstrate that these goals can be reached by modifying graphitic carbon nitride via the introduction of additional carbon atoms into its vacancy sites. We found that with the increase of carbon concentration, the band gap of graphitic carbon nitride decreases rapidly and comes to close as the carbon concentration is higher than 2.609%, thus leading to a semiconductor–metal phase transition. More interestingly, local magnetic moments appear in the triangular domain centered by the introduced carbon atom and they interact in a ferromagnetic or “antiferromagnetic” manner depending on their relative positions. The tunable band gap and ferromagnetism revealed in the carbon-modified graphitic carbon nitrides offer a promising approach to achieve applications in hydrogen generation and spintronic devices.