Unveiling the role of carbonate in nickel-based plasmonic core@shell hybrid nanostructure for photocatalytic water splitting

Though carbonates are known for several decades, their role in sun-light driven photocatalysis is still hidden. Herein, carbonate boosted solar water splitting in nickel-based plasmonic hybrid nanostructures is disclosed for the first time via in-situ experiments and density-functional theory (DFT)-based calculations. Ni@NiO/NiCO3 core@shell (shell consisting of crystalline NiO and amorphous NiCO3) nanostructure with varying size and compositions are studied for hydrogen production. The visible light absorption at ∼470 nm excludes the possibility of NiO as an active photocatalyst, emphasizing plasmon driven H2 evolution. Under white light irradiation, higher hydrogen yield of ∼80 µmol/g/h for vacuum annealed sample over pristine (∼50 µmol/g/h) complements the spectroscopic data and DFT results, uncovering amorphous NiCO3 as an active site for H2 absorption due to its unique electronic structure. This conclusion also supports the time-resolved photoluminescence results, indicating that the plasmonic electrons originating from Ni are transferred to NiCO3 via NiO. The H2 evolution rate can further be enhanced and tuned by the incorporation of NiO between Ni and NiCO3.