摘要: NiFe oxyhydroxide and hydroxide have been proven to be efficient and earth-abundant non-noble metal catalysts for the oxygen evolution reaction (OER). However, the fragile nature of these oxyhydroxides or hydroxides severely reduces the long-term stability and hinders the industrial applications. Meanwhile, the poor electrical conductivity of these materials also has seriously led to the higher overpotential when applying to the OER. Herein, a novel method using polyurethane (PU) sponge as electroplating was carried out to design NiFe alloy foam with different Fe content for OER. The physical properties of NiFe alloy foams were characterized by Scanning Electronic Microscopy (SEM), Energy Dispersive System (EDS) and X-Ray Diffraction (XRD), respectively, suggesting that the porous NiFe alloy is formed with uniform distribution of Ni and Fe. The OER performance was tested by Cyclic Voltammetry (CV), Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS), I-t, etc. The results showed that the doped Fe could significantly improve the conductivity and OER performance of Ni foam. The NiFe alloy foam with 30% Fe exhibited 292 mV overpotential at 10 mA/cm2 and the Tafel slope 126.12 mV/decade in alkaline solution with excellent long-term stability. Without any complex electrode preparation processes and binders, NiFe alloy foam is much convenient to use as anode of water splitting in alkaline media for industrial applications.
摘要: Pd-based catalysts have been widely used in alkaline fuel cells. However, up to now, the effects of oxidation treatment of Pd-based catalysts on their application in alkaline fuel cells have been rarely reported. In this paper, PdCo nano-metal catalyst was prepared by calcination-oxidation treatment. It was found that the mass specific activity and area specific activity of the resulting PdO-Co3O4 nano-composite for electrocatalytic oxidation of ethylene glycol in alkaline solution were 3.8 and 2.4 times that of commercial Pt/C, respectively. Compared with PdCo nanometals, the mass specific activity and area specific activity of the PdO-Co3O4 nanocomposite for the electrocatalytic oxidation of ethylene glycol in the alkaline solution increased by 1.6 and 1.2 times, respectively. The experimental and calculated results showed that the surface morphology and active center of the catalyst changed after calcination and oxidation treatment. The adsorption energies of O2 and OH on the Co doped PdO (101) surface decreased, which was beneficial to stabilize the intermediate C2H4OHO*. As a result, the energy barrier for the O−H dissociation on the Co-doped surface was reduced. The strong binding of Co doped PdO (101) with ethylene glycol and its intermediate species led to different electrochemical kinetics and reaction path to produce excellent electric catalytic activity. The synergistic effect of PdO and Co3O4 significantly enhanced the interaction between active oxygen and catalyst surface, which not only facilitates the formation of superoxide species on the catalyst surface, but also improves the redox properties of the catalyst and promotes the electrocatalytic oxidation activity of ethylene glycol. The strategy of bi/multi-metallic oxidation proposed in this paper provides a general methodology for the construction of other catalysts.
摘要: In this study, multi-walled carbon nanotube (MWCNTs)-SiO2 composite adsorbents MWCNTs-SiO2-2, MWCNTs-SiO2-4, MWCNTs-SiO2-6 (CS2, CS4, CS6) with molar percentages of MWCNTs of 38%, 52%, and 66% were synthesized using the sol-gel method. The effects of the MWCNT content, temperature (30−60 °C), water vapor concentration (1%−5%), and the number of cycles on the adsorption capacity of toluene were studied, and an adsorption kinetics analysis was performed. The results showed that the adsorption capacity for toluene at 30−60 °C was AC (activated carbon) < CS2 < CS4 < CS6, and the adsorption capacity of CS6 to toluene was up to 50.28 mg/g. For every 10 °C increase in temperature, the penetration time decreased by 10−20 min, and the adsorption content decreased by 3.5% for every 1% increase in water vapor concentration. The phase with the fastest mass transfer rate of toluene could be described by the quasi-secondary adsorption kinetics model, in which intraparticle diffusion plays a major role. The mole percentage of MWCNTs ranged from 38% to 66%, the higher the content was, the easier it was to adsorb toluene. The functional group types of the MWCNTs-SiO2 adsorbent after regeneration did not change, and the adsorbent maintained good adsorption performance.