Edge-passivated graphene nanoribbons as metal free photocatalyst for efficiently photocatalytic overall water splitting with sunlight.

The metal free photocatalysts have more environmentally friendly and low-cost advantages but are challenging to find suitable ones. Using the electronic properties of the edge-passivated graphene nanoribbons (EPGNRs) by manipulating the widths and edges, we demonstrate that 5 EPGNRs consisting of metal free elements, which are screened from 10 graphene nanoribbons passivated by H/N/O/F atoms, can achieve high solar-to-hydrogen efficiency in overall water splitting for hydrogen production. After ensuring the energy and thermodynamic stabilities, we construct 16 possible photocatalytic schemes for each EPGNR. At the same time, the feasible ones are selected by calculating charge density distributions, vacuum levels, and the potential energy of the band edges. 9 eligible schemes for overall water splitting are determined and the solar-to-hydrogen efficiencies are calculated according to the overpotentials and band gaps. The highest value of 34.19% is attributed to the H-GNR-O nanoribbon and a larger 38.71% can be boosted by stain engineering, which reveals that the passivated atoms can substantially manipulate the electronic properties and photocatalytic performance of graphene nanoribbons. The calculated Gibbs free energies confirm that the photocatalytic hydrogen and oxygen generations can be driven by the present EPGNRs. Therefore, the newfound metal free EPGNRs are promising for driving overall water splitting for generating hydrogen in a clean way. [Display omitted] • Photocatalytic water splitting schemes are built for five considered nanoribbons. • The highest solar-to-hydrogen efficiency of these schemes can reach 34.19%. • Anisotropic vacuum levels are responsible for the high solar-to-hydrogen efficiency. • Thermodynamic feasibility of the built schemes is ensured by the Gibbs free energies. [ABSTRACT FROM AUTHOR]