Hydrogen generation ability of B-site substituted two-dimensional Ca_n-1Ti_n-3Nb₃O_3n+1⁻ perovskite nanosheets in photoelectrochemical cell

Many semiconductor materials have been researched for hydrogen evolution application, in which 2D nanosheet materials are given a bunch of investigation due to their suitable energy band edges and proper band gap. The studying of a novel B-site substituted 2D perovskite nanosheets, Ca_n-1Ti_n-3Nb₃O_3n+1⁻ (CTNO⁻), with a layer number n = 4, 5, and 6 shows that these n-type semiconductors have unique properties with large band gaps (3.71 – 3.78 eV). These Dion-Jacobson family members, titaniobate nanosheets, are fabricated by substituting partially transition metal Ti elements into the Nb element positions (B sites) of the niobate (NbO₆) perovskite structure. A well crystalline structure and the ability in hydrogen generation are exhibited. The energy band diagrams of CTNO⁻ (n = 4, 5, and 6) nanosheets are determined and established. The photoelectrochemical devices made of B-site substituted CTNO⁻nanosheets are carried out for investigating of the ability in hydrogen generation reaction. The CTNO⁻ (n = 5) nanosheets performs the water splitting capability with the highest hydrogen generation efficiency. The hydrogen generation efficiency is improved by a p-n composite combining CTNO⁻ (n = 4, 5, and 6) nanosheets with a conductive polymer of PEDOT:PSS. The highest efficiency of hydrogen generation is belonging to CTNO⁻ (n = 4)/PEDOT:PSS with a hydrogen formation rate of 5.576 × 10² µmol h⁻¹ g⁻¹. Concerning all these performances, these Dion Jacobson phase CTNO⁻ (n = 4, 5, and 6) nanosheets are considered for ultrathin scale photoelectrochemical cell or phototransistor applications.