NaNbO₃/NaTaO₃ Superlattices: Cation-Ordering Improved Band-Edge Alignment for Water Splitting and CO₂ Photocatalysis

Abstract

Perovskite oxide heterostructures have been extensively investigated for their excellent photocatalytic properties. Here, through hybrid density functional theory calculations, we systematically investigate the formation of NaNbO 3 −NaTaO 3 (NBO-NTO) heterostructures. The sequential cations replacement in the superlattices reveals the Nb−Ta ratio range that allows the effective formation of heterostructures, which occurs through a spontaneous polarization mechanism induced by the electrostatic potential discontinuity in the interface. The resulting cation ordering is responsible for the sawtoothlike potential distribution that spatially separates valence and conduction charges and reduces the heterostructure bandgap. The symmetric NBO 5 /NTO 5 junction has the smallest bandgap (2.50 eV) whose transitions are associated with Nb 5d xy orbitals on the interfacial plane. Such a relaxation mechanism provides the heterostructure with anisotropic optical properties and interface absorption peaks closer to the visible light spectrum. The phenomena strongly suggest the use of these heterostructures in photocatalytic reactions, supported by their coherent band-edge alignment with both water splitting and CO 2 reforming potentials.

Efficient Ti3C2Tx MXene/TiO2 Hybrid Photoanodes for Dye-Sensitized Solar Cells

“…To determine the properties of Ti 3 C 2 T x /TiO 2 -based photoanodes, we performed DFT calculations. Here, the interface formation energy per unit area ( E form ) of the proposed MXene–TiO 2 heterostructure was calculated using eq : where E [TiO 2 , Ti 3 C 2 T 2 ] , E [Ti 3 C 2 T 2 ] , and E [TiO 2 ] are the total energies of the MXene–TiO 2 heterostructure, isolated MXene, and TiO 2 reference supercells, respectively, and A is the total area of the supercell. The factor 2 arises from the fact that in this nanocomposite, the supercell has two surfaces.…”

MoS2–2xSe2x Nanosheets Grown on Hollow Carbon Spheres for Enhanced Electrochemical Activity

“…Tafel slope is another fundamental factor which affects the activity of HER, which determines the rate of the reaction. ,− C@MoS 1.8 Se 0.2 exhibited the smallest Tafel slope (53.16 mV/dec in Figure e). Optimized Se doping plays an important role in improving the HER activity. ,, In the case of x = 0.1, the catalytic activity of HER of C@MoS 1.8 Se 0.2 is the highest.…”

Gel-like Ag-Dicyandiamide Metal–Organic Supramolecular Network-Derived g-C3N4 for Photocatalytic Hydrogen Generation

“…Hydrogen is considered a clean, renewable, and sustainable energy source that can replace fossil fuels in the near future. , The production of H 2 via photocatalysis using light energy is promising because solar energy is inexhaustible. However, the photocatalytic H 2 conversion efficiency is still low because of several drawbacks, including fast charge recombination and weak visible light harvesting capability. , Among different photocatalysts such as TiO 2 , ZnO, CdS, NaTaO 3 , and SrTiO 3 , g-C 3 N 4 is a metal-free polymeric semiconductor with high thermal and chemical stability, a band gap energy of approximately 2.6–2.7 eV, and a suitable redox potential for H 2 and O 2 evolution in photocatalysis systems. It is widely viewed as a promising photocatalyst candidate. − However, it has some intrinsic drawbacks such as fast charge recombination, limited optical absorption in the visible light region, and low photocatalytic efficiency (quantum efficiency = ∼0.1% at 420–460 nm), which need to be addressed.…”