This paper describes the role of SnO2 in the electronic transport of polycrystalline hematite (α‐Fe2O3). The proper sintering process allows for freezing of a state of electronic defects, in which the electrical properties of hematite are controlled by the grain boundary and Sn segregation. Impedance spectroscopy and dc conductivity measurements show that current flows through preferential pathways associated with Sn segregation that occurs at the grain boundary, leading to a decrease in grain‐boundary resistance. Atomic force microscopy and electric force microscopy measurements confirm the results of the impedance analysis. The identification of preferential grain boundaries for electrical conductivity may have a direct influence on the light‐induced water‐splitting performance of the hematite photoanode.

Novel two-dimensional non-van der Waals materials have been reported, boosting efforts to probe their properties and identify key applications. In this work, we report the synthesis, by means of a novel route via sonication of synthetic hematite, and characterization by transmission electron and atomic force microscopy of samples composed of two-dimensional hematite ([001]-cut layered α-Fe2O3). Microscopy images show a layered material with a handful of possible crystalline orientations, of which the [001] is the most abundant, presenting thickness of up to approximately 100 nm. Next, we employed first-principles calculations to study their structural stability and evaluate their thickness distribution. The stability of single, double, and triple layered structures is confirmed by phonon spectra and the formation energy is obtained, pointing out to the possibility of few layers, freestanding, stable samples. Further statistical modeling suggests that even though such thin samples are stable, their abundance is very small in comparison to thicker layers. We show that the antiferromagnetic ordering of the bulk phase is preserved in the nanostructured material, from the double-layered sample onward; however, a nonzero magnetization arises due to distinct localized moments in surface Fe atoms. Finally, our calculated band structures present narrower gaps in the layered structures in comparison to the bulk, and a charge-trapping acceptor level is identified at the surface Fe atoms.

A colloidal deposition process combined with the thermal spreading ability of Sb over hematite surface is used to obtain a mesoporous photoanode for water oxidation.

A simple approach to exfoliate and functionalize MoS2 in a single-step is described, which combines the dispersion of MoS2 in polybutadiene solution and ultrasonication processes. The great advantage of this process is that a colloidal stability of MoS2 in nonpolar solvent is achieved by chemically bonding polybutadiene on the perimeter edge sites of MoS2 sheets. In addition, elastomeric nanocomposite has been prepared with singular mechanical properties using functionalized MoS2 as nanofiller in a polybutadiene matrix with a subsequent vulcanization reaction.

Hematite is considered to be the most promising material used as a photoanode for water splitting and here we utilized a sintered hematite photoanode to address the fundamental electrical, electrochemical and photoelectrochemical behavior of this semiconductor oxide. The results presented here allowed us to conclude that the addition of Sn(4+) decreases the grain boundary resistance of the hematite polycrystalline electrode. Heat treatment in a nitrogen (N2) atmosphere also contributes to a decrease of the grain boundary resistance, supporting the evidence that the presence of oxygen is fundamental for the formation of a voltage barrier at the hematite grain boundary. The N2 atmosphere affected both doped and undoped sintered electrodes. We also observed that the heat treatment atmosphere modifies the surface states of the solid-liquid interface, changing the charge-transfer resistance. A two-step treatment, with the second being performed at a low temperature in an oxygen (O2) atmosphere, resulted in a better solid-liquid interface.