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Hydrogen production via water splitting is one of the latest low-cost green hydrogen production technologies. The challenge is to develop inexpensive and highly active catalysts. Herein, we present the preparation of electrocatalysts based on cobalt–phosphorus (Co-P) coatings with different P contents for hydrogen and oxygen evolution reactions (HER and OER). The Co-P coatings were deposited on the copper (Cu) surface using the economical and simple method of electroless metal deposition. The morphology, structure, and composition of the Co-P coatings deposited on the Cu surface were studied via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), while their activity for HER and OER in 1 M KOH was investigated using linear sweep voltammetry (LSV) and chrono-techniques. It was found that the catalyst activity for both HER and OER depends on the P content of the catalyst and varies based on the highest efficiency for each reaction. The Co-P coating with 11 wt% P exhibited the lowest overpotential value of 98.9 mV for the HER to obtain a current density of 10 mA cm−2 compared to the Co-P coatings with 8, 5, 1.6, and 0.4 wt% P (107.6, 165.9, 218.2, and 253.9 mV, respectively). In contrast, the lowest OER overpotential (378 mV) was observed for the Co-P coating with 8 wt% P to obtain a current density of 10 mA cm−2 as compared to the Co-P coatings with 5, 11, 1.6, and 0.4 wt% P (400, 413, 434, and 434 mV, respectively). These results suggest that the obtained catalysts are suitable for HER and OER in alkaline media. [ABSTRACT FROM AUTHOR] more...

The electrolysis of water is one of low-cost green hydrogen production technologies. The main challenge regarding this technology is designing and developing low-cost and high-activity catalysts. Herein, we present a strategy to fabricate flexible electrocatalysts based on nickel–iron (NiFe) alloy coatings. NiFe coatings were plated on the flexible copper-coated polyimide surface (Cu/PI) using the low-cost and straightforward electroless metal-plating method, with morpholine borane as a reducing agent. It was found that Ni90Fe10, Ni80Fe20, Ni60Fe40, and Ni30Fe70 coatings were deposited on the Cu/PI surface; then, the concentration of Fe2+ in the plating solution was 0.5, 1, 5, and 10 mM, respectively. The morphology, structure, and composition of NixFey/Cu/PI catalysts have been examined using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and inductively coupled plasma–optical emission spectroscopy (ICP-OES), whereas their activity has been investigated for hydrogen evolution (HER) and oxygen evolution (OER) reactions in 1 M KOH using linear sweep voltammetry (LSVs). It was found that the Ni80Fe20/Cu/PI catalyst exhibited the lowest overpotential value of −202.7 mV for the HER, obtaining a current density of 10 mA cm−2 compared to Ni90Fe10/Cu/PI (−211.9 mV), Ni60Fe40/Cu/PI (−276.3 mV), Ni30Fe70/Cu/PI (−278.4 mV), and Ni (−303.4 mV). On the other hand, the lowest OER overpotential (344.7 mV) was observed for the Ni60Fe40/Cu/PI catalyst, obtaining a current density of 10 mA cm−2 compared to the Ni35Fe65 (369.9 mV), Ni80Fe20 (450.2 mV), and Ni90Fe10 (454.2 mV) coatings, and Ni (532.1 mV). The developed Ni60Fe40/Cu/PI catalyst exhibit a cell potential of 1.85 V at 10 mA cm−2. The obtained catalysts seem to be suitable flexible catalysts for HER and OER in alkaline media. [ABSTRACT FROM AUTHOR] more...

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] more...

Biodiesel is one of the biofuels that has been examined the most in the research and has a promising future as a replacement for fossil fuels. A catalyst is often needed to increase the manufacture of biodiesel, which is produced by transesterification or esterification. A number of difficulties with product separation, a significant amount of wastewater effuents released from the downstream filtration, and the unwanted soap created as a result of the reaction between feedstock with a high FFA composition and homogeneous base catalysts are typical problems faced by commercially available homogeneous catalysts. The use of heterogeneous magnetic catalysts in FAME production has become a focus of interest for many researchers due to its efficient catalyst separation, high catalyst recovery rate, and shorter processing time. The development of magnetic acid and base heterogeneous catalysts, as well as their efficiency in producing biodiesel, were the primary subjects of this study. Additionally, several techniques for producing magnetic particles were evaluated. Method of heterogeneous catalysts in promoting biodiesel synthesis through transesterification procedure was also investigated. To generate more self-sustaining biodiesel industries, further investigation is needed to employ waste materials as a basis for the manufacturing of heterogeneous magnetic acid and base catalysts. Magnetic catalysts employed for FAME production. Narration provided an in-depth explanation of designing strategies for magnetic catalyst. Reusability of magnetic catalysts was studied. [ABSTRACT FROM AUTHOR] more...

The perfect strategy for the generation of green and renewable hydrogen (H2) fuels is the direct electrocatalytic splitting of plentiful seawater rather than scarce freshwater. One of the half-reactions taking place during the electrocatalytic splitting of seawater is oxygen evolution (OER). However, the OER is affected by slow four-electron transfer kinetics as well as competitive chlorine evolution reactions (CERs) in seawater. To overcome the kinematic and competitive barriers of seawater splitting and achieve an excellent overall performance of seawater splitting, we herein report a facile, low-cost, one-step fabrication procedure of 3D structured nickel–manganese (NiMn) coatings using a dynamic hydrogen bubble template (DHBT) technique. The electrocatalytic activities of the thus synthesized catalytic materials for OER in simulated seawater (0.5 M NaCl + 1 M KOH, denoted as SSW) and alkaline natural seawater (natural seawater + 1 M KOH, denoted as ASW) were investigated using linear sweep voltammetry (LSV) at varying temperatures from 25 to 75 °C. Scanning electron microscopy (SEM) and inductively coupled plasma–optical emission spectroscopy (ICP–OES) were used to examine the surface morphology and composition of the prepared catalysts. It was found that the prepared NiMn/Ti-1 catalyst in a plating bath containing a molar ratio of 1:1 Ni2+:Mn2+ and having the lowest Mn loading of 13.43 µg cm−2 exhibited quite reasonable activity for OER in Cl− ion rich SSW and ASW. To achieve the benchmark current density of 10 mA cm−2 in SSW and ASW, the NiMn/Ti-1 electrocatalyst requires overpotentials of 386 and 388 mV, respectively. In addition, this optimal bimetallic electrocatalyst also demonstrated superior long-run stability at 1.81 V (vs. RHE) and 10 mA cm−2 for 24 h in both working electrolytes. Impressively, the two-electrode electrolyzer—NiMn/Ti-5(−)||NiMn/Ti-1(+)—needs only 1.619 V to deliver 10 mA cm−2 current density for overall alkaline seawater electrolysis, which is even 0.075 V lower than the noble metal-based electrolyzer (Pt(−)||NiMn/Ti-1(+)). [ABSTRACT FROM AUTHOR] more...

In this work, 3D nickel-manganese (NiMn) bimetallic coatings have been studied as electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline (1.0 M KOH) media and the HER in acidic (0.5 M H2SO4) media. The catalysts have been deposited on a titanium substrate (1 × 1 cm2) using low-cost and facile electrochemical deposition method through a dynamic hydrogen bubble template technique. The electrocatalytic performance of these fabricated catalysts was investigated by using Linear Sweep Voltammetry (LSV) for HER and OER at different temperatures ranging from 25 up to 75 °C and also was characterized by scanning electron microscopy (SEM) and inductively coupled plasma optical emission spectroscopy (ICP-OES). It was found that fabricated NiMn/Ti-5 electrocatalyst with Ni2+/Mn2+ molar ratio of 1:5 exhibits excellent HER activity in alkaline media with overpotential of 127.1 mV to reach current density of 10 mA cm−2. On the contrary, NiMn/Ti-1 electrocatalyst that fabricated with Ni2+/Mn2+ molar proportion of 1:1 and lowest Mn-loading of 13.43 µgcm−2 demonstrates exceptional OER activity with minimum overpotential of 356.3 mV to reach current density of 10 mA cm−2. The current densities increase ca. 1.8–2.2 times with an increase in temperature from 25 °C to 75 °C for both HER and OER investigation. Both catalysts also have exhibited excellent long-term stability for 10 h at constant potentials as well as constant current density of 10 mA cm−2 that assure their robustness and higher durability regarding alkaline water splitting. [ABSTRACT FROM AUTHOR] more...

In this study, Mn-based multicomponent catalysts supported by two different carriers (lightweight expanded clay aggregate and the Ukrainian clinoptiolite) were prepared by electroless metal deposition method and tested for the selective catalytic reduction of NO with ammonia (NH3-SCR de-NO). Prior to the activity test, all the catalysts prepared were characterized by inductively coupled plasma optical emission spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray mapping, X-ray photoelectron spectroscopy, H2-TPR and NH3-TPD techniques. The particular interest of the present study was focused on the investigation of the carrier's role in the NO catalytic reduction and the promoting effect provided by the incorporation of the small amount of Pt (0.1 wt.%) in the Mn-based catalytic layer. The results revealed that the carrier's role in the NO catalytic conversion can be considered as a factor determining the effectiveness of the conversion process. Ukrainian clinoptiolite was proved to be a more attractive carrier for the preparation of the effective SCR de-NO catalysts due to its intrinsic sorption capacity, surface acidity and the redox potential. The high NO conversion efficiency provided by the Mn-based clinoptiolite-supported catalysts can be explained by the synergistic effect between the carrier and the active species deposited. It was shown that both the Mn97.6Cu2.4/clinoptiolite and the Mn97.5Co2.5/clinoptiolite catalysts can be successfully applied as the low-temperature (100–300°C) catalysts for NH3-SCR de-NO. When the NO removal efficiency varies in the range of 86–91%, the additional incorporation of Pt in the active layer in the amount of 0.1 wt.% can enhance the NO reduction by about 5% on average. [ABSTRACT FROM AUTHOR] more...