Constructing a novel metal-free g-C3N4/g-CN vdW heterostructure with enhanced visible-light-driven photocatalytic activity for water splitting

Abstract With the increasing environmental pollution and energy crisis, developing and designing environmentally friendly, low-cost, metal-free and efficient photocatalyst for water splitting is vitally important. Herein, a novel g-C3N4/g-CN van der Waals (vdW) heterostructure is proposed and its structural, electronic and optical properties are systematically investigated based on first-principles method. The results show that the g-C3N4/g-CN vdW heterostructure is a type-II semiconductor, which satisfies band gap and band edge requirements of the redox potential of water splitting. In addition, the oxygen evolution reaction (OER) on g-C3N4 side and the hydrogen evolution reaction (HER) on g-CN side can proceed spontaneously in thermodynamics. Most notably, the electronic, thermodynamic and optical properties of the g-C3N4/g-CN vdW heterostructure can be modulated by applying biaxial strain to achieve the purpose of better catalytic water splitting. Also, the good visible-light absorption intensity of the g-C3N4/g-CN vdW heterostructure can also be exhibited without strain and it is much better under strain of −2%. Consequently, these findings suggest that the g-C3N4/g-CN vdW heterostructure has a promising potential as a photocatalyst for water splitting.