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Manganese oxide catalysts, both bulk and supported on γ-Al₂O₃ and SiO₂, have been studied by Raman and FTIR spectroscopies, their phase composition being determined by X-ray diffraction. The supported catalysts were prepared via pore volume impregnation from nitrate precursors, the atomic ratio of manganese to aluminium and silicon, respectively, being in the range from 0.5/100 to 18/100. The use of Raman analysis in the microscopic configuration allowed the spectra to be taken at different points of the surface and revealed the inhomogeneity of the catalyst. Besides the Raman features of the β-MnO₂ and α-Mn₂O₃ phases, other signals were assigned to isolated Mn²⁺ ions accommodated in tetrahedral vacancies on the support surface and to some epitaxial layers of γ-Mn₂O₃ and manganese silicate, respectively. The FTIR spectra, though not as useful because of the strong bands of the support that overlap those of manganese oxides, support these findings.

In this work, the thermoelectric (TE) properties of poly(3,4-ethylenedioxylthiophene):poly(styrene sulfonate) (PEDOT:PSS) thin films at room temperature are studied. Different methods have been applied for tuning the TE properties: 1^st addition of polar solvent, dimethyl sulfoxide (DMSO), into the PEDOT:PSS solution; 2^nd post-treatment of thin films with a mixture of DMSO and ionic liquid, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄). It is verified that DMSO post-treatment is more efficient than DMSO addition in improving the electrical conductivity with a trivial change in the Seebeck coefficient. The power factor is increased up to 30.1 μW mK⁻² for the film with DMSO post-treatment, while the optimized power factor by DMSO addition is 18.2 μW mK⁻². It is shown that both DMSO addition and post-treatment induce morphological changes: an interconnected network of elongated PEDOT grains is generated, leading to higher electrical conductivity. In contrast, for those films post-treated in the presence of EMIMBF₄, an interconnected network of short and circular PEDOT grains with increased polaron density is created, resulting in the improvement in the Seebeck coefficient and a concomitant compromise in the electrical conductivity. An optimized power factor of 38.46 μW mK⁻² is achieved at 50 vol% of EMIMBF₄, which is the highest reported so far for PEDOT:PSS thin films to our knowledge. Assuming a thermal conductivity of 0.17 W mK⁻¹, the corresponding ZT is 0.068 at 300 K. These results demonstrate that post-treatment is a promising approach to enhance the TE properties of PEDOT:PSS thin films. Furthermore, ionic liquid, EMIMBF₄, shows the potential for tuning the TE properties of PEDOT:PSS thin films via a more environmentally benign process.

The engineering of acetylenic carbon-rich nanostructures has great potential in many applications, such as nanoelectronics, chemical sensors, energy storage, and conversion, etc. Here we show the synthesis of acetylenic carbon-rich nanofibers via copper-surface-mediated Glaser polycondensation of 1,3,5-triethynylbenzene on a variety of conducting (e.g., copper, graphite, fluorine-doped tin oxide, and titanium) and non-conducting (e.g., Kapton, glass, and silicon dioxide) substrates. The obtained nanofibers (with optical bandgap of 2.51 eV) exhibit photocatalytic activity in photoelectrochemical cells, yielding saturated cathodic photocurrent of ca. 10 µA cm⁻² (0.3–0 V vs. reversible hydrogen electrode). By incorporating thieno[3,2-b]thiophene units into the nanofibers, a redshift (ca. 100 nm) of light absorption edge and twofold of the photocurrent are achieved, rivalling those of state-of-the-art metal-free photocathodes (e.g., graphitic carbon nitride of 0.1–1 µA cm⁻²). This work highlights the promise of utilizing acetylenic carbon-rich materials as efficient and sustainable photocathodes for water reduction