Platinum-modified cobalt nanosheets supported on three-dimensional carbon sponge as a high-performance catalyst for hydrogen peroxide electroreduction

Carbon Nanotube-Supported Bimetallic Core-Shell (M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni)) Cathode Catalysts for H2O2 Fuel Cells

M@Pd/CNT (M: Zn, Mn, Ag, Co, V, Ni) core-shell and Pd/CNT nanoparticles were prepared by sodium borohydride reduction and explored as cathode catalysts for the hydrogen peroxide reduction reaction. Electrochemical and physical characterization techniques are applied to explore the characteristics of the produced electrocatalysts. The cyclic voltammetry (CV) experiments show that Zn@Pd/CNT-modified electrodes have a current density of 273.2 mA cm-2, which is 3.95 times higher than that of Pd/CNT. According to the chronoamperometric curves, Zn@Pd/CNT has the highest steady-state current density for the H2O2 electro-reduction process among the synthesized electrocatalysts. Moreover, electrochemical impedance spectroscopy (EIS) spectra confirmed the previous electrochemical results due to the lowest charge transfer resistance (35 Ω) with respect to other electrocatalysts.

Catalytic reduction of 4-nitrophenol and methylene blue pollutants in water by copper and nickel nanoparticles decorated polymer sponges

In the present study, two catalysts based-on copper and nickel nanoparticles anchored on agarose-coated sponge (Cu-AG-sponge and Ni-AG-sponge) were prepared, respectively. Both catalysts were characterized by analytical techniques of thermogravimetric analysis energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Spherical Cu and Ni nanoparticles on struts of AG-coated sponge were observed by FESEM and the samples' elemental composition was confirmed by EDX technique. After characterization, the Cu-AG-sponge and Ni-AG-sponge catalysts were tested in 4-nitrophenol (4-NP) and methylene blue dye (MB) reduction in an aqueous medium. The reduction of the 4-NP to 4-aminophenol (4-AP) was achieved up to 95% using the NaBH₄ reductant and Cu-AG-sponge and Ni-AG-sponge catalysts, respectively. Similarly, the rate of reduction of MB was faster for the Cu-AG-sponge as compared to the Ni-AG-sponge which was discussed based-on the catalyst morphology and other factors. The high rate of reactions for the 4-NP and MB reduction suggests that the Cu-AG-sponge and Ni-AG-sponge catalyst possess high catalytic efficiency, low cost and good reusability having the potential to be used in similar other reactions.

Recent Developments for the Application of 3D Structured Material Nickel Foam and Graphene Foam in Direct Liquid Fuel Cells and Electrolyzers

Platinum and platinum-based catalysts are some of the most effective catalysts used in fuel cells. However, electrocatalysts used for direct liquid fuel cells (DLFCs) and electrolyzers are high cost and suffer from several other problems, thus hindering their commercialization as power sources to produce clean energy. Common issues in electrocatalysts are low stability and durability, slow kinetics, catalyst poisoning, high catalyst loading, high cost of the catalytic materials, poisoning of the electrocatalysts, and formation of intermediate products during electrochemical reactions. The use of catalyst supports can enhance the catalytic activity and stability of the power sources. Thus, nickel foam and graphene foam with 3D structures have advantages over other catalyst supports. This paper presents the application of nickel foam and graphene foam as catalyst supports that enhance the activities, selectivity, efficiency, specific surface area, and exposure of the active sites of DLFCs. Selected recent studies on the use of foam in electrolyzers are also presented.

Preparation of a Sulfur-Functionalized Microporous Polymer Sponge and In Situ Growth of Silver Nanoparticles: A Compressible Monolithic Catalyst

We report a compressible monolithic catalyst based on a microporous organic polymer (MOP) sponge. The monolithic MOP sponge was synthesized via Sonogashira-Hagihara coupling reaction between 1,4-diiodotetrafluorobenzene and 1,3,5-triethynylbenzene in a cosolvent of toluene and TEA (2:1, v/v) without stirring. The MOP sponge had an intriguing microstructure, where tubular polymer fibers having a diameter of hundreds of nanometers were entangled. It showed hierarchical porosity with a Brunauer-Emmett-Teller (BET) surface area of 512 m² g^-1. The MOP sponge was functionalized with sulfur groups by the thiol-yne reaction. The functionalized MOP sponge exhibited a higher BET surface area than the MOP sponge by 13% due to the increase in the total pore and micropore volumes. A MOP sponge-Ag heterogeneous catalyst (S-MOPS-Ag) was prepared by in situ growth of silver nanoparticles inside the sulfur-functionalized MOP sponge by the reduction of Ag⁺ ions. The catalytic activity of S-MOPS-Ag was investigated for the reduction reaction of 4-nitrophenol in an aqueous condition. When S-MOPS-Ag was compressed and released during the reaction, the rate of the reaction was considerably increased. S-MOPS-Ag was easily removed from the reaction mixture owing to its monolithic character and was reused after washing and drying.

Preparation method of Ni@Pt/C nanocatalyst affects the performance of direct borohydride-hydrogen peroxide fuel cell: Improved power density and increased catalytic oxidation of borohydride

The Ni@Pt/C electrocatalysts were synthesized using two different methods: with sodium dodecyl sulfate (SDS) and without SDS. The metal loading in synthesized nanocatalysts was 20wt% and the molar ratio of Ni: Pt was 1:1. The structural characterizations of Ni@Pt/C electrocatalysts were investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM). The electrocatalytic activity of Ni@Pt/C electrocatalysts toward BH₄^- oxidation in alkaline medium was studied by means of cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results showed that Ni@Pt/C electrocatalyst synthesized without SDS has superior catalytic activity toward borohydride oxidation (22016.92Ag_Pt^-1) in comparison with a catalyst prepared in the presence of SDS (17766.15Ag_Pt^-1) in NaBH₄ 0.1M at 25°C. The Membrane Electrode Assembly (MEA) used in fuel cell set-up was fabricated with catalyst-coated membrane (CCM) technique. The effect of Ni@Pt/C catalysts prepared with two methods as anode catalyst on the performance of direct borohydride-hydrogen peroxide fuel cell was studied. The maximum power density was obtained using Ni@Pt/C catalyst synthesized without SDS at 60°C, 1M NaBH₄ and 2M H₂O₂ (133.38mWcm^-2).

Facile preparation of three-dimensional Ni(OH)2/Ni foam anode with low cost and its application in a direct urea fuel cell

The nano-sheet Ni(OH)₂/Ni foam electrode exhibits superior catalytic activity and stability towards urea electro-oxidation and shows a good fuel cell performance.

The optimal design of Co catalyst morphology on a three-dimensional carbon sponge with low cost, inducing better sodium borohydride electrooxidation activity

A low-cost nano-flake Co@carbon sponge (Co NF@carbon sponge) electrode is prepared by a simple sponge carbonization method coupled with direct Co growth on the carbon sponge surface using pulsed electrodeposition.

Palladium dispersed in three-dimensional polyaniline networks as the catalyst for hydrogen peroxide electro-reduction in an acidic medium

A novel Pd/polyaniline/CFC electrode is prepared by electroless deposition of palladium (Pd) onto three-dimensional polyaniline networks.