Nitrogen doped ultrathin calcium/sodium niobate perovskite nanosheets for photocatalytic water oxidation

The present study combines the advantages of chemical exfoliation and elemental doping to have enhanced surface area, better charge carrier separation and extended light absorption in N³⁻/Nb⁴⁺ co-doped nanosheets, which were employed for the first time to study their O₂ evolution response. The Dion-Jacobson phase, KCa₂NaNb₄O₁₃ perovskite was calcined under NH₃ environment at various reaction durations (5 hr, 6 hr, 7 hr) to yield N³⁻/Nb⁴⁺ co-doped layered structures and subsequently exfoliated into ultrathin nanosheets. The N³⁻/Nb⁴⁺ co-doped nanosheets realized superior visible light absorption and bandgap narrowing as determined from UV–visible spectroscopy profiles. The synthesis of bulk materials and ultrathin morphology of exfoliated nanosheets were confirmed through XRD, SEM and AFM. The chemical states of the elements were examined by XPS measurements. The optimized N³⁻/Nb⁴⁺ co-doped CNNO^--6hr nanosheets demonstrated excellent O₂ evolution of 903 μmol g^-1 after 4 h compared to N³⁻/Nb⁴⁺ co-doped CNNO^--5hr (510 μmol g^-1), N³⁻/Nb⁴⁺ co-doped CNNO^--7hr (528 μmol g^-1) and non-doped CNNO^- nanosheets (381 μmol g^-1). Our study paves a way on the feasibility of combining various chemical strategies for advanced photocatalyst design.