Harvesting urbach tail energy of ultrathin amorphous nickel oxide for solar -driven overall water splitting up to 680 nm

Harvesting near infrared light for water splitting opens up a new avenue in solar conversion but suffers from the low photon energy. Towards this, amorphous a-NiOx is reported to exhibit strong long-wavelength urbach tail absorption and provide abundant oxidation active sites due to its disordered structure. And its intrinsic twodimensional ultrathin structure shortens the migration distance of photoinduced carriers. This enlightens water splitting under 680 nm red light when combined with electron captures like reduced graphene oxide. Furthermore, a-NiOx||C3N4 heterojunction is constructed to extend the light response from UV to near infrared region, together with a built-in-electric field to facilitate interfacial charge separation. The unique structure achieves stoichiometric water splitting under simulated sunlight with an apparent quantum efficiency of 6.2 % at 420 nm, outperforming most state-of-art photocatalysts. This work may bring new opportunities in modulating amorphous materials for artificial photocatalysis.

Automated summary

A study shows that amorphous nickel oxide (a-NiOx) has the ability to absorb long-wavelength light, enabling water splitting when combined with electron captures like reduced graphene oxide. Constructing a-NiOx||C3N4 heterojunction can efficiently achieve stoichiometric water splitting under simulated sunlight.