Dion-Jacobson Phase Perovskite Ca₂Na_n-3Nb_nO_{3 n+1}^-(n = 4-6) Nanosheets as High-κ Photovoltaic Electrode Materials in a Solar Water-Splitting Cell

A well-crystalline two-dimensional (2D) perovskite material, Ca2Nan-3NbnO3n+1- (CNNO-) nanosheets, derived from the Dion-Jacobson phase has the potential to generate hydrogen through photoelectrochemical water splitting. Here, we demonstrate that a high-κ photovoltaic electrode consisting of CNNO- nanosheets with layer number n = 4-6 and a hole-transport polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), can form a p-n junction and an overall solar-to-hydrogen water-splitting cell, with the highest efficiency of 0.52% and a hydrogen evolution rate of 80.64 μmol h-1. First-principles calculations are carried out to confirm the energy-band diagram of this promising material, which significantly affects the electronic transition process in a solar water-splitting cell. 2D CNNO- nanosheets present great potential for serving as nanoelectronic water-splitting devices in single transistors.