Metal-free highly-efficient photocatalysts for overall water splitting: C3N5 multilayers
As a promising means of renewable energy storage, producing molecular hydrogen and oxygen from photocatalytic water splitting has gained increasing interest. The optimal photocatalyst for water splitting should have high solar energy conversion efficiency and strong photocatalytic redox ability to driven hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, few photocatalyst has been reported to fulfill these two contradictive requirements. Here, we demonstrated from first-principles that the recently synthesized two-dimensional carbon nitride (C3N5) multilayers can serve as promising candidates to reach this goal. The intrinsic electric field which is more pronounced in multilayers alters the band alignment of the photocatalysts, making the HER and OER proceed driven solely by the photogenerated carriers. The thickness-dependent electronic band gap (2.95-2.16 eV) along with the high carrier mobility broadens the energy range of light adsorption and promotes the carrier separation and transfer, leading to high solar energy conversion efficiency. Our computational results offer not only low-cost, earth-abundant and environmentally friendly photocatalysts but also a promising strategy for the design of photocatalysts for highly-efficient overall water splitting without using sacrificial reagents.