Donor density and surface states of Fe ₂ O ₃ via Sn doping control the water oxidation and onset potential.

TiO ₂ underlayer effectively suppresses the charge recombination at FTO/α-Fe ₂ O ₃ interface and also acts as a source of Ti ⁴⁺ dopants when sintered at high temperature (800 °C).

For ex-situ co-doping methods, sintering at high temperatures enables rapid diffusion of Sn⁴⁺ and Be²⁺ dopants into hematite (α–Fe₂O₃) lattices, without altering the nanorod morphology or damaging their crystallinity. Sn/Be co-doping results in a remarkable enhancement in photocurrent (1.7 mA/cm²) compared to pristine α–Fe₂O₃ (0.7 mA/cm²), and Sn⁴⁺ mono-doped α-Fe₂O₃ photoanodes (1.0 mA/cm²). From first-principles calculations, we found that Sn⁴⁺ doping induced a shallow donor level below the conduction band minimum, which does not contribute to increase electrical conductivity and photocurrent because of its localized nature. Additionally, Sn⁴⁺-doping induce local micro-strain and a decreased Fe-O bond ordering. When Be²⁺ was co-doped with Sn⁴⁺-doped α–Fe₂O₃ photoanodes, the conduction band recovered its original state, without localized impurities peaks, also a reduction in micro-strain and increased Fe-O bond ordering is observed. Also the sequence in which the ex-situ co-doping is carried out is very crucial, as Be/Sn co-doping sequence induces many under-coordinated O atoms resulting in a higher micro-strain and lower charge separation efficiency resulting undesired electron recombination. Here, we perform a detailed systematic characterization using XRD, FESEM, XPS and comprehensive electrochemical and photoelectrochemical studies, along with sophisticated synchrotron diffraction studies and extended X-ray absorption fine structure.

A novel, three-dimensional, ternary CdS/ZnIn₂S₄/TiO₂ heterojunction has been fabricated via a three-step facile hydrothermal method.