Raman spectroscopy and surface-enhanced Raman scattering (SERS) provide complementary insights into molecular structure and molecule–metal interactions. We compare the solution Raman and potential-dependent SERS spectra of methylene blue (MB+) with calculations for free MB+ and an MB+/Ag40 adsorption model. Cyclic voltammetry on Au and Ag screen-printed electrodes distinguishes the dye’s redox response from the dominant Ag/AgCl processes accompanying electrochemical activation. The voltammograms do not directly demonstrate the formation of a particular SERS-active nanostructure on the present electrode; the proposed chloride-mediated restructuring is supported by previous microscopic studies. The experimental SERS spectra vary with potential, and potential-resolved Raman measurements reveal the evolving response of the interface. A band-position-based comparison with nine Raman-relevant MB+/Ag40 reference modes avoids quantitative use of the calculated Raman intensities. When requiring at least seven matched bands within ±30 cm−1, 23 of 29 spectra fulfilled the criterion; the smallest mean absolute wavenumber deviation (MAE = 9.38 cm−1; RMSE = 12.26 cm−1) occurred at −0.289 V versus the Ag pseudo-reference (8/9 matched bands). This minimum denotes the closest band-position agreement with the static reference, and is not interpreted as evidence for a unique adsorption geometry or oxidation state. Independent two-dimensional FDTD calculations illustrate x-polarization-selective field localization in idealized 2 nm Ag junctions; the field maps have not been demonstrated to converge, so these results are illustrative rather than predictive of experimental SERS enhancement. The main experimental observation is a potential-dependent MB SERS response occurring alongside pronounced Ag/AgCl electrochemistry; a specific surface morphology or causal enhancement mechanism cannot be established from the voltammograms alone. Together, these observations provide a complementary molecular and electromagnetic perspective on a coupled, potential-dependent Ag/AgCl–methylene blue interface, rather than separating the contributions of the molecules and the substrate. The absolute potential assignment is also restricted by the use of a printed Ag pseudo-reference, as its potential cannot be assumed to remain constant during cycling in a chloride-containing electrolyte. A significant limitation of the current EC-SERS protocol is that electrochemical activation of the Ag surface and the redox conversion of methylene blue occur within overlapping potential ranges. Consequently, the cathodic formation of the SERS-active Ag nanostructure can coincide with the reduction of MB+ to reduced methylene blue species. Consequently, spectra acquired during the cathodic scan cannot be uniquely assigned to MB+ on the basis of the electrode potential alone, and the present data do not allow molecular redox chemistry to be experimentally separated from substrate reconstruction.
This work reports the synthesis of the organic–inorganic copper chloride perovskite (C6H5CH2NH3)2[CuCl4] and its application as an electrode material for lithium-ion batteries. Hybrid copper halide perovskites have emerged as environmentally friendly alternatives to lead-based systems due to their structural versatility and chemical stability; however, their electrochemical energy storage properties remain largely unexplored. To the best of our knowledge, this is the first report investigating (C6H5CH2NH3)2[CuCl4] as an electrode material for lithium-ion batteries. The structural and morphological characteristics of the material were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (IR), confirming the formation of a layered perovskite structure. Electrochemical performance was evaluated by cyclic voltammetry and galvanostatic charge–discharge measurements. The material delivered an initial specific capacity of 114 mAh g−1 at a current density of 20 mA g−1 and maintained a coulombic efficiency around 99% after 100 cycles, indicating good cycling stability. The electrochemical behavior suggests that the reversible redox activity of Cu species contributes significantly to the charge storage mechanism. Postmortem XRD analysis revealed that the original perovskite framework was only partially retained after cycling, as several characteristic diffraction peaks remained while others disappeared, indicating partial structural decomposition. These results highlight the potential of chlorocuprate-based hybrid perovskites as alternative electrode materials for lithium-ion batteries.
The conversion of hydrogen into electricity is a subject of intense interest. Various technologies are available at laboratory level, but in industrial applications, the most established of them is the proton exchange membrane-based fuel cell. This increased interest, combined with the maturity of the technology, has led to attempts to integrate fuel cells into hybrid systems with renewable energy sources. Such hybrid systems are subject to numerous studies, most of which are aimed at optimizing installed capacity in order to reduce the cost of energy production, of investment, etc. This article aims to provide an experiment-based approach for a simple yet accurate model linking electrical power with hydrogen consumption that can be used in the design and optimization procedures for hybrid systems. For this purpose, an experimental setup with a 1 kW fuel cell was built at the Technical University of Sofia, where experimental studies were conducted to enable the development of the model. Although the proposed model does not reflect the influence of certain technological factors on the operation of the fuel cell, it provides sufficient accuracy to determine the hydrogen consumption for a given electrical power when used in operation simulations of the hybrid system.
Additive manufacturing provides a fabrication route for electrode components with controlled macrostructure; however, printable carbon inks that also incorporate oxygen reduction reaction active precursors remain underdeveloped. Here, XC-72 carbon was combined with selected metal precursors to prepare N–C, Fe–N–C, and Pt-containing carbon ink formulations for direct ink writing. The precursor mixtures were incorporated into a polyurethane-based matrix, pyrolyzed at 900 °C, and characterized using X-ray diffraction, oscillatory rheology, rotating ring-disk electrode measurements, Brunauer–Emmett–Teller surface-area analysis, and scanning electron microscopy. XRD confirmed retention of carbon diffraction features and the formation of metal-containing crystalline phases after pyrolysis. Oscillatory rheology showed storage moduli exceeding loss moduli for the tested formulations, indicating elastic-dominant behavior suitable for shape retention during printing. For the PGM-free formulations, incorporation of nitrogen and iron precursors improved ORR onset potential, half-wave potential, limiting current density, and electron-transfer selectivity relative to the carbon control. BET analysis showed a decrease in accessible surface area after precursor incorporation, consistent with partial pore blocking or structural modification during pyrolysis. These results establish a printable formulation platform for ORR-active carbon-based inks, while future work is required to isolate the effects of printed architecture, pore hierarchy, and durability under fuel-cell operating conditions.
Photoelectrochemical (PEC) energy conversion is a promising approach for solar-to-chemical fuel production, but its practical performance is limited by insufficient visible-light utilization and charge-carrier recombination. Here, poly(3,4-ethylenedioxythiophene) (PEDOT)-centered TiO2 hybrid electrodes were prepared by electropolymerizing PEDOT on FTO substrates, followed by electrochemical doping/dedoping treatment and coating with commercial TiO2 as a model oxide semiconductor. SEM, EDS, and LIBS analyses confirmed the successful deposition of TiO2 onto PEDOT-based films. Four-probe measurements showed that electrochemical doping reduced the apparent resistance of PEDOT-based electrodes, while UV–vis spectroscopy revealed enhanced long-wavelength absorption for doped PEDOT-containing films. PEC measurements using TiO2, PEDOT, and TiO2–PEDOT electrodes showed that PEDOT-containing electrodes exhibited much stronger photoresponses than commercial TiO2 alone under both HER- and OER-relevant conditions. The TiO2–PEDOT electrode showed stable photocurrent responses under chopped illumination and retained photoresponse under illumination transmitted through a 410 nm UV-cut filter, supporting the primary role of PEDOT in visible-light utilization. Long-term chronoamperometry further showed that TiO2–PEDOT retained approximately 99.0% of its cathodic current under HER-relevant conditions and 91.9% of its anodic current under OER-relevant conditions after 5200 s of continuous illumination. The improved response of TiO2–PEDOT compared with PEDOT alone suggests that TiO2/PEDOT physical contact may assist interfacial charge separation and transport. These findings demonstrate that PEDOT-centered metal oxide/conducting polymer hybrids provide a useful model platform for visible-light-responsive PEC energy-conversion applications.
