Effects of potassium ions and platinum cocatalysts on the photocatalytic performance of Poly(Heptazine Imides)

•The structures and electronic properties of K-PHI and H-PHI are compared.•A systematic theoretical study of the structure, electronic and optical properties and photocatalytic hydrogen evolution reaction activity of K-PHI and H-PHI loaded Pt cocatalysts was conducted.•The short-range induced dipole effect of K+ and the larger size of the Pt cocatalyst together promote the photocatalytic performance of carbon nitride.