A comparison study of molten-salt and solid-state method for the photoelectrochemical water splitting performance of Dion-Jacobson layers perovskite Ca₂Na_n-3Nb_nO_3n+1^- (n = 4, 5, and 6) nanosheets

Solar energy is one of the elements that have been used as a resource in the green energy field. Hydrogen, as an energy carrier, can be produced from many kinds of sources, including solar energy. Here, we present two-dimensional (2D)perovskite material derived from the Dion-Jacobson phase (DJ), Ca₂Na_n-3Nb_nO_3n+1^- (CNNO⁻) nanosheets, with the number of layer n = 4–6 synthesized via microwave-assisted hydrothermal method. The starting material KCa₂Nb₃O₁₀ (KCNO) is made from two methods. The solid-state calcination KCNO product has more than two-phase, while the molten-salt synthesis produces a well cubic KCNO crystalline. TThe thickness of the 2D CNNO⁻ nanosheets is increasing, in dependence on the n value. Meanwhile, the estimated optical band gap is decreasing, in dependence on the n value. 2D CNNO⁻ nanosheets show the absorbance under ultraviolet (UV) light, which confirms their semiconducting nature. The capability of these 2D nanosheets to generate hydrogen is presented via photo-electrochemical (PEC) water splitting. The molten-salt fabricated CNNO⁻ nanosheets CNNO6 shows better performance with the highest efficiency ɳ up to 0.110% when applied to the PEC device.