A new strategy of preparing uniform graphitic carbon nitride films for photoelectrochemical application

In the present work, we report on a two-step vapor deposition (TVD) process of depositing graphitic carbon nitride (g-CN) films for photoelectrochemical (PEC) application. The method is versatile for various monomers including cyanamide, dicyanamide and melamine as well as different substrates. The role of deposition temperature and amount of monomers has been investigated in detail. Structural and surface morphological studies suggest uniform and pinhole-free g-CN films could be achieved with this feasible method. Photon-induced oxygen evolution upon anodic polarization in aqueous electrolytes brings up a photocurrent density of 63 μA cm−2 for the g-CN films prepared with dicyanamide. This is the highest value to date for a pristine g-CN photoanode at the bias of 1.23 V (versus reversible hydrogen electrode) without sacrificial reagents. The good performance could be attributed to an enhanced light harvesting and decreased charge transport resistance at the film/electrolyte interface with an increase of amount of monomers. Accordingly, the strategy of TVD brings g-CN another step to applying as photoactive material in various photoelectronic fields. Furthermore, this method can also be easily extended to synthesis of heterojunction in the second-step of TVD process by choosing proper substrates to further enhance the PEC properties.

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