Plasma-mediated fabrication of ultrathin NiAl nanosheets having rich oxygen vacancies and doped nitrogen sites and their utilization for high activity and robust stability in photoelectrochemical water oxidation

Abstract

Layered double hydroxides (LDHs) are promising photocatalysts for water oxidation, essential to generate solar fuels, but their limited accessible reaction sites, slow charge transfer, and activity degradation are yet to be overcome. As a solution to overcome these drawbacks, we report nanosheets of mono or dual layers derived via nitrogen plasma exfoliation of anion layers from NiAl LDHs. Moreover, such a sheet has rich O vacancies resulting in decreased Ni–O and shortened Ni–metal bonds. Furthermore, doped nitrogen leads to metal–N and N–O bonds along with oxynitrides. With O vacancies facilitating adsorption of water oxidation intermediates onto low-coordinated Ni and the doped N pulling electrons from water oxidation intermediates, the ultrathin nanosheets assembled on hematite nanorods are found to outperform the activity of hematite by about 2 fold and the charge transfer of LDH nanoplates assembled on hematite by about 4 fold, while showing excellent activity retention close to 100% in a long-term stability test.