Nepal Academy of Science and Technology (NAST), previously RONAST, is an autonomous apex body established in 1982 to promote science and technology in Nepal. With the implementation of federal structure by the government of Nepal, it has opened its first provincial office at Mahendranagar.
Solid oxide fuel cells (SOFCs) are efficient energy conversion devices essential to clean energy development, yet their broad application is limited by material challenges, including sluggish oxygen reduction kinetics at intermediate temperatures, electrode instability and vulnerability to contaminants. High-entropy oxides, a novel class of materials characterized by multiple principal elements and high configurational entropy, present a promising approach to overcome these issues via their distinctive “four core effects”. This review begins with the fundamentals of high-entropy oxides, covering their definition, phase stabilization mechanisms, and relevant descriptors, then systematically reviews their progress as SOFC cathodes, electrolytes, and anodes. Key advances are summarized, and current challenges are analyzed, offering guidance for the design of high-performance and stable high-entropy oxides for SOFCs.
The development of efficient and stable intermediate-temperature solid oxide fuel cells (SOFCs) necessitates high-performance cathode materials that are cobalt-free, cost-effective, and compatible with proton-conducting electrolytes. While Sr2Fe2O6 (SFO)-based ferrites offer a promising cobalt-free alternative, their electrochemical performance requires further enhancement to compete with state-of-the-art cathodes. This study proposes and validates a multi-element doping strategy as a superior approach to tailor the properties of SFO. The specific oxide Sr2Fe1.5Mo0.125Sn0.125Sc0.125Zr0.125O6 (SFO-ZSSM) is designed, synthesized via a solid-state reaction method, and systematically evaluated as a cathode for proton-conducting SOFCs (H-SOFCs). Its performance is benchmarked against a series of SFO cathodes modified with single dopants (Mo, Sn, Sc, Zr). Structural characterization confirms the successful formation of a phase-pure perovskite structure with homogeneous elemental distribution. Electrical conductivity relaxation (ECR) measurements reveal that SFO-ZSSM exhibits dramatically enhanced oxygen and proton transport kinetics compared to all singly-doped counterparts, demonstrating a significant synergistic effect. Consequently, fuel cells employing the SFO-ZSSM cathode deliver exceptional peak power densities of 1580, 1137, and 854 mW cm-2 at 700, 650, and 600 degrees C, respectively, significantly outperforming cells with single-doped cathodes. Electrochemical impedance spectroscopy further corroborates its superior catalytic activity, showing the lowest polarization resistance. Moreover, the SFO-ZSSM cell demonstrates excellent operational stability over 100 h, attributed to its robust microstructure and Ba-free composition. This work conclusively establishes the multi-element doping strategy as a highly effective pathway for engineering high-performance, cobalt-free cathodes for next-generation H-SOFCs.
Groundwater arsenic contamination poses a global threat to human and animal health, driving extensive research into effective remediation technologies. To simultaneously address the challenges of arsenic pollution and sludge disposal, this study proposed a novel strategy to convert waste sludge into a Fe/Mn modified biochar (F1M2BC) for enhanced As(III) removal. Characterization and adsorption experiments demonstrated that with an optimal Fe:Mn molar ratio of 1:2, F1M2BC possessed a high specific surface area and abundant mesoporous structure. The adsorption process followed pseudo-first-order kinetics (R2 = 0.983) and the Langmuir model (R2 = 0.988), suggesting homogeneous monolayer adsorption, with a maximum capacity of 33.28 mg/g at 298 K. It also exhibited excellent reusability, maintaining about 85% removal efficiency and 86.31% regeneration efficiency over five adsorption-desorption cycles. Importantly, the maximum concentration of leached Mn (0.082 mg/L) remained below the 0.1 mg/L threshold stipulated by the standards for drinking water quality. The removal of As(III) by F1M2BC was mainly achieved through the efficient synergy of manganese and iron: The surface manganese oxides oxidize As(III) to As(V), and then the generated As(V) is stabilized and fixed by forming inner-layer complexes with the active sites of iron oxides. In addition, various mechanisms such as pore filling, electrostatic interactions, and hydrogen bonds also play auxiliary roles in the overall removal of arsenic. In this study, we developed a Fe/Mn modified sludge based biochar that provides a closed loop solution for treating arsenic contaminated groundwater, offering a dual solution that transforms disposal liabilities into valuable water purification materials while addressing both contamination cleanup and resource conservation.
BACKGROUND:Hospital wastewater (HWW) serves as a critical reservoir for antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), especially those conferring resistance to quinolones, fluoroquinolones and macrolides. This study investigated the prevalence and seasonal dynamics of ARB and ARGs in HWW from the Kathmandu Valley, Nepal. METHODS:We collected and analysed 16 untreated HWW samples from eight hospitals during the summer and winter seasons (2022-2023). Physicochemical parameters, prevalence of ARB, selected ARGs (qnrS, aac(6')-Ib-cr, erm(B)) and class 1 integron (intI1) were assessed. Results were compared by hospital type and season. RESULTS:Significant seasonal differences were observed in temperature (P = 0.00024) and total suspended solids (P = 0.042). Klebsiella pneumoniae (31.67%) and Escherichia coli (28.33%) were the most frequently isolated ARB. K. pneumoniae exhibited very high resistance to ciprofloxacin (97.74%) and levofloxacin (89.47%). Among the targeted genes, the aac(6')-Ib-cr gene was the most prevalent (55.67%), followed by intI1 (50%), qnrS (25%) and erm(B) (11.67%). The erm(B) gene was significantly more prevalent in medium-sized hospitals (P = 0.001). No significant seasonal variation was observed for ARGs or the mobile genetic elements (P > 0.05). Although not statistically significant, strong correlations were observed between qnrS prevalence and pH (ρ = 0.912) and ammonia (ρ = 0.812), suggesting potential environmental influences on the dissemination of resistance. CONCLUSION:The HWW is a significant antimicrobial resistance reservoir, emphasizing improved wastewater treatment and antibiotic stewardship to mitigate resistance dissemination.
