In this work, a multicomponent platinum electrocatalyst supported on carbon (PtX/(SbY + SnO2Z)/C) was synthesized for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) for a proton exchange membrane fuel cell (PEMFC). Specific surface area analysis and scanning electron microscopy studies confirmed the incorporation of antimony and tin dioxide nanoparticles into the electrocatalyst structure. Electrochemical studies made it possible to differentiate the contribution of the modifiers to the characteristics of the modified electrocatalyst. Due to the incorporation of tin dioxide, the specific activity values in the oxygen reduction and methanol oxidation reactions exceed those of the unmodified samples by 40 and 36%, respectively. The introduction of antimony contributed to the retention of high electrochemical characteristics (20% less loss of active surface area) upon exposure to catalytic poisons by increasing electrical conductivity. The multicomponent electrocatalyst is also characterized by a 2.8-fold increase in stability and an electrochemically active surface area comparable to that of a commercial sample.
Viscose fibers were converted into activated carbon materials by physical activation with water vapor or CO2, yielding VFH2O and VFCO2 with similar textural properties but markedly different surface chemistries. Their adsorption performance toward malathion (MLT) and its more toxic oxidation product, malaoxon (MOX), was systematically evaluated. Adsorption equilibrium was reached within approximately 60 min, and the pseudo-second-order model provided the most consistent description of the kinetic data. Equilibrium adsorption was analyzed using the Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich models. For MLT, both Freundlich and Langmuir models showed excellent agreement with the experimental data, whereas MOX model fits were more system-dependent, particularly on VFCO2. Temperature effects were also system-dependent: for MLT, Langmuir qmax decreased with temperature on VFH2O but increased on VFCO2, despite a simultaneous decrease in KL on the latter. Thermodynamic analysis over 25–40 °C yielded negative ΔG° values for all systems and negative apparent ΔH° values, indicating thermodynamically favorable adsorption with an exothermic contribution over the investigated range. Under flow-through conditions, useful removal was observed only for MLT. The results highlight the importance of adsorbent surface chemistry, pesticide structure, and operating conditions in organophosphate adsorption.
This study investigates the adsorption behavior and separation performance of CH4/CO2 binary mixtures on commercial activated carbons under conditions relevant to biogas upgrading. Adsorption isotherms of a binary CH4/CO2 mixture (60% CH4/40% CO2, v/v), selected as a model mixture relevant to biogas upgrading, were measured at 303.15 K using a high-pressure manometric system coupled with gas chromatography. All investigated materials exhibited preferential adsorption of CO2 over CH4 (SCO2/CH4 > 1), adsorption performance strongly influenced by both textural properties and surface chemistry. While ROx 0.8 showed the highest selectivity (SCO2/CH4 = 6.57), the adsorption capacity was found to be primarily governed by micropore volume and BET surface area, while CNR-115 showed a more balanced adsorption behavior with lower CH4 co-adsorption, leading to improved overall performance. To provide a more application-oriented evaluation, a methane-penalized performance indicator (API*) was introduced, combining CO2 uptake, selectivity, and methane co-adsorption into a single metric. This approach revealed that CNR-115 exhibits the best overall performance, despite not having the highest selectivity, due to its lower CH4 uptake and balanced physicochemical properties. The results highlight the importance of considering both adsorption capacity and methane preservation when selecting adsorbents for biogas upgrading. This work provides insights into structure–performance relationships and proposes a criterion for the evaluation and optimization of carbon-based adsorbents for CO2/CH4 separation.
Diesel exhaust soot (DES), a hazardous by-product of incomplete diesel combustion, was valorized into activated nanocarbon (ANC) through phosphoric acid activation for phenol removal from water. The synthesized ANC was characterized by FTIR, XRD, FE-SEM, TEM, EDX, and AFM. The results revealed predominantly spherical nanoparticles with an average size below 30 nm, a turbostratic carbon structure, and oxygen-containing surface functional groups favorable for adsorption. The adsorption performance was evaluated as a function of adsorbent dosage, contact time, initial phenol concentration, and temperature. The optimum adsorbent dosage and equilibrium time were 0.1 g and 90 min, respectively, while the highest removal efficiency was obtained at an initial phenol concentration of 10 mg L−1. The equilibrium data were best described by the Langmuir model (R2 = 0.999), with a maximum adsorption capacity of 23.98 mg g−1, indicating predominantly monolayer adsorption. Thermodynamic analysis confirmed that phenol adsorption was spontaneous (ΔG = −22.42 to −25.79 kJ mol−1) and endothermic (ΔH = +11.43 kJ mol−1), with a positive entropy change (ΔS° = +113.47 J mol−1 K−1). These findings demonstrate the potential of DES as a low-cost precursor for functional nanocarbon adsorbents and provide a sustainable approach for converting combustion waste into a value-added material for water purification.
Carbon nanotube (CNT) cathodes offer compact size, rapid response, and simplified thermal management, making them promising for stationary tomosynthesis and computed tomography (CT). In this study, we improved the high-purity production process for small-diameter multi-walled CNTs and developed a novel five-state cathode fabrication process based on electrophoretic deposition. This process increased the field-emission current while enabling the reproducible fabrication of cathodes with high consistency. The resulting multi-beam X-ray source, integrating eight cathodes, operated stably at an anode voltage of 110 kV, a pulse width of 5 ms, and a set cathode current of 40 mA (anode current: 25 mA), with an actual current deviation of less than 0.5% among the cathodes and a gate-control-voltage deviation of less than 3.7%. An eight-angle imaging test and 200 h operation (5.76 × 106 pulses) demonstrated that the tube can provide high-resolution imaging, rapid multi-angle acquisition, and stable long-term operation, thereby demonstrating potential for commercial applications. To the best of our knowledge, this study is the first to demonstrate both highly consistent fabrication of high-current CNT cathodes and sustained high-current operation of a multi-beam X-ray tube, providing a key hardware platform for development on stationary tomosynthesis and CT, and may facilitate further advances in medical imaging technology.
