Self-assembled sulphur doped carbon nitride for photocatalytic water reforming of methanol

The ability to effectively harness and store renewable solar energy in chemical forms, e.g., methanol has been widely recognised as a promising and sustainable strategy for H2 storage. Though traditional steam reforming of methanol enables effective H2 release from methanol and water, the harsh operating conditions result in high energy consumption and CO by-product. To minimize CO emission and maximise H2 production, photocatalytic liquid water reforming of methanol has been developed to produce H2 by sulphur doped graphitic carbon nitride (SCN) in this work. Consequently, both H2 and carbon dioxide (CO2) can be evolved in an ideal ratio of 3:1 and H2 yield has been found to be dependent on pH and the reaction temperature. A stable and reproducible H2 evolution rate of 14.7 mmol g-1h−1 from water/methanol over 95 h without CO evolution has been achieved, with an apparent quantum efficiency (AQE) of c.a. 30 % at 365 nm. The sulphur was found to exist as N-S-H and C-S-H bonds in the SCN photocatalysts, while the latter was found to be well correlated to the photocatalytic activity of H2 production. Such sulfur doping narrows the bandgap and offers enhanced charge separation, thus leading to enhanced photocatalytic activity.