Abstract: As a renewable energy source, solar energy holds significant potential for addressing future energy and environmental challenges. Concurrently, hydrogen (H2), as a clean and renewable energy carrier, has garnered substantial attention. Photoelectrocatalytic water splitting to produce H2 represents an emerging green technology for converting solar energy into hydrogen energy, which has been highly valued by researchers. The key to advancing this technology lies in identifying photoelectrode materials with high catalytic activity and stability. In this study, dendritic α-Fe was synthesized via electrodeposition, and the photoelectrocatalytic performance of α-Fe2O3@Fe was enhanced through partial oxidation. This approach effectively addressed the issue of the short carrier transport distance in α-Fe2O3. Specifically, dendritic α-Fe2O3 was partially oxidized after annealing at 300°C for 6 h. The resulting partially oxidized α-Fe2O3@Fe exhibited a photocurrent that was 2.23 times higher than that of the fully oxidized counterpart. The influence of deposition potential on the photoelectrocatalytic performance was systematically explored, and an optimal deposition potential was identified. Additionally, surface modification with Pt was employed to further improve the photocatalytic performance of α-Fe2O3. After continuous operation for 2 h, the photocurrent of the surface-modified sample decreased by only 6.5%, indicating a substantial enhancement in stability.

Abstract: In this work, poly(3-dodecylthiophene) (P3DDT) thin films were electrochemically synthesized using tetraethylammonium tetrafluoroborate (Et4NBF4) electrolyte. After synthesis, the films were deposited onto fluorine-doped tin oxide (FTO) substrates and subjected to optical and electrical characterizations to investigate their photophysical and electronic properties. Optical analyses were performed using ultraviolet-visible absorption spectroscopy (UV-Vis), photoluminescence spectroscopy (PL), emission ellipsometry (EE) and Raman spectroscopy. The results revealed the formation of distinct structures during the electropolymerization process, which significantly affected the optical behavior observed in the UV-Vis and PL spectra. Furthermore, the EE measurements provided insights into the impact of these structures on the polarization states of emitted and transmitted light, on energy and charge transfer mechanisms, and on the photophysical behavior of P3DDT. Variations in the degree of polarization (P), anisotropy factor (r), and asymmetry factor (g) were analyzed as a function of the emission wavelength. The results confirm the potential of P3DDT as an active layer in electroluminescent devices, as the emissive material used in the active layer consisted exclusively of this polymer.

Abstract: An electrochemical analysis of the corrosion resistance of the Al-alloy EN AW-5454-D and its welded joints made by MIG (Metal Inert Gas) and by laser hybrid (LH) welding, was performed on this study. All the tested samples had a thickness of 4 mm, whereby all the samples` surfaces were cleaned with a plasma cleaning process before the elec-trochemical testing to reduce the impact of contamination. The electrochemical be-haviour was investigated in a 3.5 wt.% NaCl solution over immersion periods of 1 hour, 7 days and 30 days, using electrochemical techniques and surface analysis. The ob-tained results show that the welding processes (MIG and LH) caused microstructural heterogeneities that reduce the corrosion resistance of the weld. The MIG welded Al-alloy showed worse properties than the LH welded in the electrochemical tests, as it had a higher corrosion current density, lower polarisation resistance and higher layer capacitance. Due to long-term exposure to the immersion solution, despite the reduced susceptibility to uniform corrosion, the Al-alloy samples and their welds remained susceptible to pitting corrosion.

Abstract: In this study the photocatalytic activity as a function of effective irradiance, photocatalytic quantum yield and reactant coverage was thoroughly assessed for the proper photoreactor (PhR) selection. PhR selection is a preponderant stage for photocatalytic processes, which has been an aspect not studied in detail in various scientific investigations. The emitted wavelength and effective irradiance of several PhRs, equipped with fluorescent and light emitting diodes (LEDs) lamps, were tested in the photodegradation of methylene blue (MB) in solid phase using AgTiC. Among all tested PhRs the one equipped with the low-pressure Hg lamp enhanced the photodegradation of MB. The above is due to the Hg lamp emitted UV-type radiation, which promotes the simultaneous photoactivation of the TiO2 and the surface plasmon resonance phenomenon of the Ag nanoparticles. Based on this study, it was determined that high values of effective irradiance promoted photocata-lytic activity because of the greater amount of photogenerated species [e-/h+]. Also, the ef-fective irradiance on the proper photocatalytic material slows down the recombination rate of the [e-/h+]. A kinetic photocatalytic model (KPM) was proposed to the description of photocatalytic reactions as a function of the effective irradiance, photocatalytic quantum yield and reactant coverage considering photocatalytic pseudo steady state according to the reactant equilibrium coverage (Langmuir isotherm) and the transfer processes of the photoinduced charge carrier species.

Abstract: Ni@TiO₂ core–shell nanoparticles were synthesized by magnetron sputtering and their structure verified by HRTEM and EDS analysis. The thermal stability of these particles was investigated using in situ TEM annealing and compared with that of pure Ni nanoparticles. While pure Ni particles sinter already at 450 °C and exhibit significant growth at 800 °C, Ni@TiO2 nanoparticles remain stable up to 700 °C, with the sintering onset between 700 and 800 °C. A simple thermal-mismatch model was applied to explain the stabilizing effect of the TiO2 shell, demonstrating that differences in thermal expansion between Ni and TiO2 generate interface stresses sufficient to crack the shell after the amorphous–rutile transformation. The TiO2 coating effectively delays Ni coalescence by 250 °C relative to bare Ni, highlighting its role as a protective shell against high-temperature sintering.

Abstract:

The development of efficient, earth abundant electrocatalysts for the oxygen evolution reaction (OER) is essential for alkaline water electrolysis. In this work, we prepared ferrite, tungstate, and ferrite@tungstate heterostructure by simple co-precipitation and hydrothermal routes and evaluated them as OER catalysts in 1 M KOH. The catalysts are characterized by XRD, UV–Vis, FTIR, SEM, and EDX. The catalysts exhibit phase-pure components with intimate contact between the two phases, and a smaller particle size for the composite. The ferrite@tungstate exhibits modified electronic structure possibly due to the electronic interaction between Fe and W centers. Electrochemical measurements demonstrated an overpotential of 200 mV at 10 mA cm-2, that exhibits a reduced Tafel slope (150 mV dec⁻¹), and displays lower charge-transfer resistance than the single-phase oxides. In addition, the composite retains >94% of its current over 24 h, indicating good durability. These results suggest that ferrite–tungstate coupling can be an effective strategy to non-noble OER catalysts.