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Gold and silver nanoparticles in different atomic ratios deposited on reduced graphene oxide (AuAg/rGO-1, AuAg/rGO-2, and AuAg/rGO-3) were tested for the borohydride oxidation reaction in an alkaline medium. The morphology, structure, and composition of AuAg/rGO electrodes were investigated by transmission electron microscopy (TEM) and scanning electron microscopy with integrated energy dispersive spectroscopy (SEM-EDS). The TEM analysis showed that the most of gold and silver particles (more than 80%) are up to 9 nm in size, while slightly larger particles represent less than 5%. SEM-EDS showed a similar morphology, and the composition of three AuAg/rGO electrodes was determined. AuAg/rGO-1 and AuAg/rGO-2 electrodes showed similar, while AuAg/rGO-3 electrodes demonstrated slightly lower electrocatalytic activity for borohydride oxidation. The studied electrodes were observed to be active for the borohydride hydrolysis as well, which is expected based on literature data. AuAg/rGO certainly represent potential anode materials for application in direct borohydride fuel cells.

Protected areas can only deliver their environmental, social and economic benefits if they are effectively managed. The aim of the paper is to analyze the management of nature parks entrusted to the State Enterprise for Forest Management “Srbijašume”, identify management problems and opportunities, and provide management and other reform proposals in order to improve the efficiency of management of protected areas. SE “Srbijašume” manages 5 nature parks on an area of 280,497 ha, which makes up 94% of the total area of nature parks in Serbia. Managerial organization of protected areas in SE “Srbijašume” is in accordance with the Law on Nature Protection, which prescribes the conditions that must be met by the manager in terms of professional, personnel and organizational qualifications to perform the tasks of protection, improvement, promotion and sustainable development of the protected areas. The management of protected areas is coordinated with the three-level organizational structure of the Enterprise (General Directorate, Forest Estates, Forest Administrations). For the management of nature parks “Stara planina”, “Golija”, “Zlatibor” and “Radan” special work units have been formed.

Design and development of novel, low-cost and efficient electrocatalysts for oxygen evolution reaction (OER) in alkaline media is crucial for lowering the reaction overpotential and thus decreasing the energy input during the water electrolysis process. Herein, we present the synthesis of new 14-membered bis-thiosemicarbazide and bis-isothiosemicarbazide macrocycles and their nickel(II) complexes characterized by spectroscopic techniques (1H and 13C NMR, IR, UV–vis), electrospray ionization mass spectrometry, single crystal X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) and cyclic voltammetry. Finally, the activity of nickel(II) complexes towards OER is reported. NiIILSEt delivered a current density of 10 mA cm−2 at the lowest overpotential of 350 mV with the lowest Tafel slope of 93 mV dec−1. The high performance of NiIILSEt might be attributed to its high surface area and thus abundant active sites with the observed low charge-transfer resistance enabling the effective current flow through the electrocatalyst. Square-planar coordination geometry and increment in Ni oxidation state are believed to favor its OER performance. Beside high activity towards OER, NiIILSEt demonstrated excellent long-term stability with continuous operation, advocating its possible application in commercial systems. [ABSTRACT FROM AUTHOR]

Environmental pollution due to the excessive consumption of fossil fuels for energy production is a critical global issue. Fuel cells convert chemical energy directly into electricity in a clean and silent electrochemical process, but face challenges related to hydrogen storage, handling, and transportation. The direct borohydride fuel cell (DBFC), utilizing sodium borohydride as a liquid fuel, is a promising alternative to overcome such issues but requires the design of cost-effective nanostructured electrocatalysts. In this study, we synthesized nitrogen-doped graphene anchoring Ni nanoparticles (Ni@NG) by thermal degradation of polyethylene terephthalate bottle waste with urea and metallic Ni, and evaluated it as a sustainable carbon support. Electrocatalysts were prepared by incorporating ultralow amounts (0.09 to 0.27 wt.%) of Pd into the Ni@NG support. The resulting PdNi@NG electrocatalysts were characterized using ICP-OES, XPS, TEM, N2-sorption analysis, XRD, and Raman and FTIR spectroscopy. Voltammetry assessed the materials' electrocatalytic activity for oxygen reduction and borohydride oxidation reactions in alkaline media, corresponding to the anodic and cathodic reactions in DBFCs. The electrocatalyst with 0.27 wt.% Pd loading (PdNi_15@NG) exhibited the best performance for both reactions. Consequently, it was employed as an anodic and cathodic material in a lab-scale DBFC, achieving a specific power of 3.46 kW gPd−1. [ABSTRACT FROM AUTHOR]

We present the synthesis and characterization of two monometallic coordination polymers, [Co(L)2(H2O)2]n (Co-CP) and [Ni(L)2(H2O)2]n (Ni-CP), alongside a heterobimetallic counterpart, CoNi-CP, derived from an amide-based multifunctional pro-ligand 4-(pyrimidin-5-ylcarbamoyl)benzoic acid (HL), and discussed their electrocatalytic activity in the oxygen evolution reaction (OER). The CPs were characterized using various techniques, including elemental analysis, IR spectroscopy, X-ray diffraction, and thermal and powder XRD analyses. The low-cost amide-functionalized transition metal pristine coordination polymers Co-CP and Ni-CP were demonstrated to catalyze the OER in alkaline media, surpassing the benchmark IrO2 electrocatalyst performance. The heterometallic coordination polymer (CoNi-CP) displayed a lower Tafel slope value (and thus, faster kinetics) and higher long-term durability compared to its monometallic counterparts, Co-CP and Ni-CP. The results obtained show a pristine transition metal heterobimetallic coordination polymer as a lowcost electrocatalyst of great promise and high performance for OER catalysis in alkaline media. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) with transition metals (Co, Cu, Fe, Mn, Ni) of Keggin structure and lamellar-stacked multi-layer morphology were synthesized. They were subsequently explored as bifunctional electrocatalysts for oxygen electrodes, i.e., oxygen reduction (ORR) and evolution (OER) reaction, for aqueous rechargeable metal-air batteries in alkaline media. The lowest Tafel slope (85 mV dec−1) value and the highest OER current density of 93.8 mA cm−2 were obtained for the Fe-POM electrocatalyst. Similar OER electrochemical catalytic activity was noticed for the Co-POM electrocatalyst. This behavior was confirmed by electrochemical impedance spectroscopy, where Fe-POM gave the lowest charge transfer resistance of 3.35 Ω, followed by Co-POM with Rct of 15.04 Ω, during the OER. Additionally, Tafel slope values of 85 and 109 mV dec−1 were calculated for Fe-POM and Co-POM, respectively, during the ORR. The ORR at Fe-POM proceeded by mixed two- and four-electron pathways, while ORR at Co-POM proceeded exclusively by the four-electron pathway. Finally, capacitance studies were conducted on the synthesized POMs. [ABSTRACT FROM AUTHOR]

An ion-exchange procedure of synthetic zeolite ZSM-5 (Si/Al = 15) was used to prepare three cobalt ZSM-5 zeolites (CoM-ZSM5 (M = Zn and Ni)) that were examined for OERs in alkaline media. The structural, morphological, and surface properties of the prepared materials were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, and low-temperature nitrogen adsorption. All three electrocatalysts showed OER activity where CoNi-ZSM5 presented the highest current density (9.5 mA cm−2 at 2 V), the lowest Tafel slope (134 mV dec−1), and the lowest resistances of the charge transfer reaction (31.5 Ω). Overpotential (ηonset) at an onset potential of 410 mV for both CoNi-ZSM5 and Co-ZSM5 and 440 mV for CoZn-ZSM5 electrodes was observed. Co-ZSM5 showed somewhat lower OER catalytic activity than CoNi-ZSM5, while CoZn-ZSM5 demonstrated the lowest OER catalytic activity. The Rct of CoZn-ZSM5 is significantly higher than the Rct of CoNi-ZSM5, which could lead to their different OER activities. Good OER stability and low price are the main advantages of the synthesized CoM-ZSM5 samples in this study. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction (OER) electrocatalysts are frequently made from noble metal-based oxides like ruthenium/iridium oxides. However, because of their scarcity and high price, researchers are now focusing on creating innovative OER catalysts based on affordable transition metals that have improved electrical conductivity and accessibility to active sites. Metal–organic frameworks (MOFs), a unique class of inorganic materials with excellent physical and chemical properties, have witnessed significant progress in promising green energy systems. In this work, a novel mixed-ligand metal–organic framework [Co(μ-1κN,2κN′-BDP)(μ3-1κoo′,2κo′′2κo′′′-BTC)]n·nH2O (BDP = boron-dipyrromethene or BODIPY; BTC = benzene tricarboxylate) denoted as CoBDPMOF has been synthesized, and its composites with different carbon materials have been designed. Compared to the pristine MOF, the composites showed enhanced electrocatalytic activity toward the oxygen evolution reaction (OER) in alkaline media. In addition, the CoBDPMOF with activated carbon showed the highest OER performance with a low Tafel slope (82 mV dec−1) and the highest j600 (59.8 mA cm−2), outperforming noble metal IrO2, the OER benchmark electrocatalyst. This study presents new insights into the design and application of CoBDPMOF-based materials for energy conversion and suggests promising avenues for further research and development in electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing bifunctional oxygen electrode materials with superior activity for oxygen reduction (ORR) and oxygen evolution (OER) reactions is essential for advancing regenerative fuel cell and rechargeable metal–air battery technologies. This present work deals with the synthesis and characterization of electrocatalysts containing Pt and Ni nanoparticles supported on nitrogen-doped mixed metal oxides (Mn2O3-NiO) and the systematic evaluation of their bifunctional ORR/OER performance in an alkaline medium. These electrocatalysts have been successfully synthesized by a simple and fast microwave method. PtNi/Mn2O3-NiO-N with a binary metal oxide-to-N ratio of 1:2 demonstrated the best performance among the studied materials regarding bifunctional electrocatalytic activity (∆E = 0.96 V) and robust stability. [ABSTRACT FROM AUTHOR]