Structural Evolution of Ni-Based Co-Catalysts on [Ca₂Nb₃O₁₀]⁻ Nanosheets during Heating and Their Photocatalytic Properties

Nickel compounds are among the most frequently used co-catalysts for photocatalytic water splitting. By loading Ni(II) precursors, submonolayer Ni(OH)₂ was uniformly distributed onto photocatalytic [Ca₂Nb₃O₁₀]⁻ nanosheets. Further heating of the nanocomposite was studied both ex situ in various gas environments and in situ under vacuum in the scanning transmission electron microscope. During heating in non-oxidative environments including H₂, argon and vacuum, Ni nanoparticles form at ≥200 °C, and they undergo Ostwald ripening at ≥500 °C. High resolution imaging and electron energy loss spectroscopy revealed a NiO shell around the Ni core. Ni loading of up to 3 wt% was demonstrated to enhance the rates of photocatalytic hydrogen evolution. After heat treatment, a further increase in the reaction rate can be achieved thanks to the Ni core/NiO shell nanoparticles and their large separation. View Full-Text