Combinatorial Studies on Wet-Chemical Synthesized Ti-Doped α‑Fe₂O₃: How Does Ti⁴⁺ Improve Photoelectrochemical Activity?

Hematite (α-Fe₂O₃)-based photoanode for photoelectrochemical water oxidation has been intensively studied for decades. Doping with isovalent or aliovalent ions is one way to mitigate several intrinsic drawbacks of bare hematite. While addition of Ti in the bulk has been reported for improving photoresponse, several aspects of effects of Ti impregnation have not been justified. In this work, Ti:Fe₂O₃ nanoellipsoids synthesized by a facile one-pot hydrothermal process present improved photoelectrochemical response. Tuned symmetry of Fe–O and Fe–Fe (Fe–Ti) with less recombination during charge transportation, tuned electron configuration of O_2p-Fe_4s4p hybridization in Ti-adjoining regime with enhanced electron relaxation within Fe₂O₃ lattice, suppressed O₂/H₂O back reaction (reduction of O₂), and inhibit formation of surface defects during hydrothermal synthesis were attested by X-ray absorption spectroscopy, Mott–Schottky analysis, and photoelectrochemical impedance spectroscopy. Additionally, Ti:Fe₂O₃ showed enhanced light absorption. Hydrogen evolution rate of 11.76 μmol h^–1 cm^–2 under illumination was observed while using Ti:Fe₂O₃ as the working electrode. Additional experiments on Mn⁴⁺ and In³⁺ incorporation showed mixed effects. This study provides insights and clarification toward “Ti-doping” of the hematite photoanode for solar hydrogen production from water

Comparative Study on the Morphology-Dependent Performance of Various CuO Nanostructures as Anode Materials for Sodium-Ion Batteries

In this work, CuO samples with three different nanostructures, i.e., nanoflakes, nanoellipsoids, and nanorods, are successfully synthesized by a facile and environmentally friendly hydrothermal approach based on the use of different structure directing agents. The morphological influence on the anodic electrochemical performances, such as capacity, cycling stability, rate capability, and diffusion coefficient measurements of these different CuO nanostructures is comparatively investigated for sodium-ion batteries. The capacity and cycling stability are higher for the CuO nanorods (CuO-NRs) based electrode as compared to the cases of CuO nanoellipsoids (CuO-NEs) and CuO nanoflakes (CuO-NFs). At a low current density of 25 mA g^–1, the CuO-NRs based electrode exhibits an excellent reversible capacity of 600 mA h g^–1. It also exhibits a capacity of 206 mA h g^–1 after 150 cycles with a capacity retention of 73% even at a higher current density of 1000 mA g^–1. The exceptional performance of CuO-NRs is attributable to its slim nanorod morphology with a smaller particle size that provides a short diffusion path and the maximized surface area facilitating good diffusion in electrolytes, ensuring good electronic conductivity and cycling stability. The comparative analysis of these materials can provide valuable insights to design hierarchical nanostructures with distinct morphology to achieve better materials designed for sodium-ion batteries