Unconventional gas-based bottom-up, meter-area-scale fabrication of hydrogen-bond free g-CN nanorod arrays and coupling layers with TiO2 toward high-efficiency photoelectrochemical performance

Meter-scale uniform g-CN nanorod (NR) arrays were directly grown on an FTO glass using an unprecedented vacuum magnetic filtered arc ion plating system for enhanced photoelectrochemical (PEC) performance. The construction of the g-CN film is based on the substrate deposition of the direct reaction of ionized carbon and nitrogen species, a gas-based bottom-up approach, distinctly different from the traditional powder deposition and thermal vapor pathways. The g-CN film exhibits obvious advantages over conventional ones in the application of PEC: (1) direct reaction of C and N species allows the formation of the g-CN without intralayer hydrogen bonds, which significantly reduces intralayer photo-generated charge carriers transfer resistance; (2) the g-CN exhibits the NR array structure and comprises considerably numerous layers stacking by stacking and vertically standing on the FTO substrate, which facilitates the photogenerated charges transfer and increases the contact area with electrolyte; (3) the robust mechanical strength of the g-CN NR film with the FTO substrate not only favors the effective charge transport but also allows long-term practical application against abrasion; (4) the gas-based bottom-up approach enables the g-CN to easily couple with, including but not limited to, TiO2 NR array to form heterostructures to further improve charge separation.