Hard template synthesis and photocatalytic activity of graphitic carbon nitride in the hydrogen evolution reaction using organic acids as electron donors

•g-C3N4 was prepared by melamine pyrolysis in the presence of silica hard templates.•The obtained samples are highly active in the H2 evolution under visible light.•Oxalic acid was found to be an effective environmentally friendly sacrificial donor.•Up to 300 μmol H2/h*gphotocat. was obtained over g-C3N4 in 1 M oxalic acid solution.