Double Perovskite Structure Induced by Co Addition to PbTiO₃: Insights from DFT and Experimental Solid-State NMR Spectroscopy

Abstract

The effects of Co addition on the chemical and electronic structure of PbTiO 3 were explored both by theory and through experiment. Cobalt was incorporated to PbTiO 3 during sol gel process. The XRD data of the compounds confirmed the perovskite structure for the pure samples. The XRD lines broadened and showed emerging cubiclike features as the Co incorporation increased. The changes in the XRD pattern were interpreted as double perovskite structure formation. 207 Pb NMR measurements revealed a growing isotropic component in the presence of Co. In line with the experiments, DFT calculated chemical-shift values corroborate isotropic coordination of Pb suggesting the formation of cubic Pb 2 CoTiO 6 domains in the prepared samples. The state-of-the-art hybrid functional first-principles calculations indicate formation of Pb 2 CoTiO 6 with cubic structure and confirms that Co addition can decrease oxygen binding energy significantly. Experimental UV-Vis spectroscopy results indicate that upon addition of Co, the band gap is shifted towards visible wavelengths which was confirmed by the energy bands and absorption spectra calculations. The oxygen binding energies were determined by temperature programmed reduction (TPR) measurements. Upon addition of Co, TPR lines shifted to lower temperatures and new features appeared in the TPR patterns. This shift was interpreted as weakening of oxygen cobalt bond strength. The change in the electronic structure by the alterations of oxygen vacancy formation energy and bond lengths upon Co insertion are determined by DFT calculations.

Hydrogenated Cs2AgBiBr6 for significantly improved efficiency of lead-free inorganic double perovskite solar cell

“…On the other side, reducing the bandgap E g of perovskite has been achieved in several reports. For example, Mete et al found that doping of Co into PbTiO 3 perovskite could effectively increase the light absorption property 32 . By doping Tl + , Tl 3+ , Sb 3+ or Sn 2+ elements into the lattice of Cs 2 AgBiBr 6 , the bandgap has been found to decrease effectively 33 – 35 .…”

Elucidating the Barriers on Direct Water Splitting: Key Role of Oxygen Vacancy Density and Coordination over PbTiO3 and TiO2

“…The calculated electronic band gaps of pristine PbTiO 3 and TiO 2 are 2.53 eV (exp. 2.5 eV) and 2.77 eV (exp. 3.1 eV), respectively.…”

“…2.5 eV) and 2.77 eV (exp. 3.1 eV), respectively. A 4 × 8 × 1 k -point mesh was used for Brillouin zone integrations.…”

Strategies to Enhance Interfacial Spatial Charge Separation for High‐Efficiency Photocatalytic Overall Water‐Splitting: A Review

“…Even if the photocatalyst has the appropriate band positions for water splitting, it may not be a suitable candidate if it does not absorb light in the visible range, as nearly half of the solar energy reaching the Earth's surface falls within the visible-light region. [60][61][62][63] Therefore, it is crucial to develop strategies to enhance light absorption, such as doping the semiconductor [64,65] coupling the photocatalyst with a sensitizer [65,66] and creating defect sites, [67] such as oxygen vacancy sites, lattice defects, and inter-band states, [68,69] and utilization of up-conversion process. [2] These methods can improve light absorption and enhance the semiconductor's photocatalytic activity, ultimately leading to more efficient water splitting.…”