The capacitance and operating voltage of supercapacitors as well as their energy density have been increased by development of different materials and electrolytes. In this paper, two strategies, for the first time, were used to improve energy density: Mn₃O₄- and N-dual doped carbon electrode and aqueous mixture of multivalent ions as electrolyte. Mn₃O₄- and N-dual doped carbon was prepared by a novel and cost-effective procedure using deep eutectic solvent. XRD, XPS, and FTIR confirmed presence of Mn₃O₄ and nitrogen, while SEM and EDS elemental mapping showed micrometer-sized nanosheets with uniform distribution of C, O, N, and Mn atoms. Charge storage behavior of carbon was tested in aqueous multivalent-based electrolytes and their mixture (Ca²⁺-Al³⁺). Regarding both specific capacitance and workable voltage, the Ca²⁺-Al³⁺ mixed electrolyte was found as the best optimal solution. The calcium addition to the Al-electrolyte allows the higher operating voltage than in the case of individual Al(NO₃)₃ electrolyte while the addition of Al³⁺ ion in the Ca(NO₃)₂ electrolyte improves the multivalent-ion charge storage ability of carbon. As a result, the specific energy density of two-electrode Mn₃O₄@N-doped carbon//Al(NO₃)₂+Ca(NO₃)₂//Mn₃O₄@N-doped carbon supercapacitor (34 Wh kg⁻¹ at 0.1 A g⁻¹) overpasses the reported values obtained for Mn-based carbon supercapacitors using conventional aqueous electrolytes.

Green hydrogen produced by alkaline electrolysis is a promising solution to address the world’s increasing energy demand while mitigating greenhouse gas emissions. However, the efficient and cost-effective production of green hydrogen via alkaline electrolysis requires improvements. This paper presents an in situ activation process that simplifies the alkaline electrolysis technology while enhancing the catalytic activity of electrodes for the hydrogen evolution reaction. The aim of this research is to enhance the energy efficiency of alkaline electrolysis and decrease the energy consumption for hydrogen production. To achieve this goal, ionic activators comprising Ni, Zn, and Mo were incorporated into the standard electrolyte solution. Our results demonstrate that the anticipated improvement in the catalytic activity of the d-metal combination, surpassing even that of precious metals, has been successfully attained. As a result, a 20% reduction in energy consumption (REC) for the hydrogen produced has been observed. The catalytic activity of the added activators for the hydrogen evolution reaction was discussed by analyzing the mechanism of the reaction via Tafel analysis and EIS techniques. These findings offer a promising approach to improve alkaline electrolysis and enhance the production of green hydrogen.

Due to intensive urbanization, global warming, and increasing energy demands, the impact of urban heat islands is becoming more significant. This study investigates the contribution of vehicular emissions to air pollution and its effects on urban heat island intensity in a selected area of Belgrade, Serbia, between March and September 2015, using a combination of experimental measurements and numerical simulations. Furthermore, this study presents the results of the research on the impact of assessment of traffic-induced air pollution on the appearance of thermal islands in the urban environment, as well as the characterization of thermal islands and their quantification. This study quantifies the effects of traffic-related emissions and urban meteorological parameters on the intensity of the urban heat island by combining field measurements with a validated three-dimensional numerical model and shows that higher traffic density increases pollutant concentrations and cooling energy demand in buildings. The study includes experimental measurements of traffic intensity and modeling of gas emissions from major roads. Using long-term and short-term field measurements, concentrations of carbon dioxide and other pollutants were analyzed with meteorological parameters and their cumulative impact to assess their impact on local air quality. A three-dimensional numerical model for simulating the dispersion of pollutants has been developed, confirmed and validated by experimental data. The results highlight a direct correlation between traffic density and pollutant concentrations, emphasizing the need for strategic urban planning and sustainable transport policies to mitigate the effects of air pollution. A validated numerical model was used to simulate dynamic changes in temperature fields and carbon dioxide concentrations caused by vehicular emissions. The findings reveal that the Urban Heat Island Intensity (UHII) for the selected area in Belgrade reached peaks of up to 12 °C during the summer measurement period, with typical values in July ranging from 5 °C to 9 °C. Furthermore, the validated numerical model demonstrated that the removal of urban trees would lead to a local air temperature increase of 1.5 °C to 3 °C, quantifying the significant cooling potential of green infrastructure. These results highlight a direct correlation between traffic density, pollutant concentrations, and the intensification of urban heat islands, emphasizing the need for strategic urban planning. Furthermore, the findings reveal that increased traffic not only elevates air pollutant levels but also enhances the intensity of urban heat islands, leading to higher cooling energy demands in buildings. These insights are vital for developing effective mitigation strategies to improve the sustainability of urban environments and living conditions. These findings provide a clear directive for urban planners: the integration and preservation of green infrastructure is a highly effective UHI mitigation strategy, capable of reducing local temperatures by 1.5–3 °C. Furthermore, the results strongly support the implementation of targeted traffic management policies in dense urban cores as a dual strategy to improve air quality and reduce local thermal loads.