Photocatalytic Hydrogen Evolution from Silica‐Templated Polymeric Graphitic Carbon Nitride–Is the Surface Area Important?

Low‐surface‐area, mesoporous silica‐templated polymeric graphitic carbon nitride (SBA–g‐C 3 N 4 ), when irradiated with visible light, exhibits a greatly improved photocatalytic hydrogen evolution rate as compared to that of conventional bulk g‐C 3 N 4 synthesized directly from the condensation of dicyandiamide. It also performs very similarly to high‐surface‐area mesoporous g‐C 3 N 4 on a per‐unit mass basis. However, on the per‐unit area basis it greatly outperforms the other materials. The intrinsically high surface activity of SBA–g‐C 3 N 4 was confirmed by using two different co‐catalysts, in situ photodeposited Pt and a structurally well‐defined molecular cobaloxime. Instead of the magnitude of the surface area as the dominant feature that determines activity, it was established that the high activity of SBA–g‐C 3 N 4 results from a much higher number of delocalized electrons present and a suppressed recombination probability of photogenerated electron–hole pairs.