Abstract
Pd nanoparticles have been generated by performing an electroless procedure on a mixed ceria (CeO
2
)/carbon black (Vulcan XC‐72) support. The resulting material, Pd–CeO
2
/C, has been ...characterized by means of transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroscopy (ICP–AES), and X‐ray diffraction (XRD) techniques. Electrodes coated with Pd–CeO
2
/C have been scrutinized for the oxidation of ethanol in alkaline media in half cells as well as in passive and active direct ethanol fuel cells (DEFCs). Membrane electrode assemblies have been fabricated using Pd–CeO
2
/C anodes, proprietary FeCo cathodes, and Tokuyama anion‐exchange membranes. The monoplanar passive and active DEFCs have been fed with aqueous solutions of 10 wt % ethanol and 2
M
KOH, supplying power densities as high as 66 mW cm
−2
at 25 °C and 140 mW cm
−2
at 80 °C. A comparison with a standard anode electrocatalyst containing Pd nanoparticles (Pd/C) has shown that, at even metal loading and experimental conditions, the energy released by the cells with the Pd–CeO
2
/C electrocatalyst is twice as much as that supplied by the cells with the Pd/C electrocatalyst. A cyclic voltammetry study has shown that the co‐support ceria contributes to the remarkable decrease of the onset oxidation potential of ethanol. It is proposed that ceria promotes the formation at low potentials of species adsorbed on Pd, Pd
I
‐OH
ads
, that are responsible for ethanol oxidation.
Electrooxidation of organics using electrons as oxidants is a clean approach to produce commodity chemicals. However, designing an electrocatalyst with superior performance at low cell voltage ...remains a challenge. In this study, a series of VS-Co@Co9S8 electrocatalysts were fabricated by thermal reduction method using MOFs as templates. The catalytic oxidation performance and reaction mechanism of such specimens for benzyl alcohol were comprehensively analyzed by electrochemical measurement method and ex-situ structure characterization. The results show that Co@Co9S8-30 M has a unique three-dimensional (3D) micro cubic structure with abundant S vacancy (VS). These features accelerate the electrons and substrate transfer as well as provide plentiful active sites for benzyl alcohol electrooxidation reaction (BAOR). Consequently, the Co@Co9S8-30 M presented outstanding catalytic activity. The overpotential of 10 mA cm−2 (η10) was only 265.4 mV for BAOR. The conversion rate and benzoic acid selectivity were achieved to 72% and 90%, respectively. Particularly, the formation rate of benzoic acid was 7.247 mmol·gcat.−1·h−1. Moreover, the Co@Co9S8-30 M exhibited superior durability over 135 h. The coordination number of octahedral metal sites in Co9S8 did not match the number of Co 3 d orbital electrons, resulting in the weakening of bonding strength between Co and S elements. Thus, the Co@Co9S8 was reconstructed to Co3O4@CoOOH. Based on this assessment, the Co3O4@CoOOH was the active site of BAOR. This work provides theoretical guidance for the design of Co-based catalysts.
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A bi-functional electrode material of self-supporting N-doped C foam grown Pd nanoparticles (Pd@N/C-8 foam) for NaBH4 electrooxidation and H2O2 reduction reaction is successfully prepared. The ...Pd@N/C-8 foam electrode is fabricated by sacrificial template synthesis of N/C foam followed by 8 repetitive Pd impregnation reduction cycles. The Pd@N/C-8 foam electrode exhibits an extraordinary catalytic performance (642 mA cm−2 at −0.2 V) in 2 mol L−1 NaOH and 0.3 mol L−1 NaBH4, which is due to the large electrochemical active surface area, low activation energy (Ea = 10.34 kJ mol−1) and 60.83% utilization efficiency of NaBH4. Besides, its catalytic density for H2O2 electroreduction reaches 648 mA cm−2 at −0.2 V in 2 mol L−1 H2SO4 +1.3 mol L−1 H2O2. The kinetic parameters show that the electrooxidation of BH4− and the electroreduction of H2O2 on Pd@N/C-8 foam electrode are first-order reactions, and the number of transferred electrons are 5.8 and 1.56, respectively. Further exploration of Pd@N/C-8 foam electrode on the direct sodium borohydride-hydrogen peroxide fuel cell (DBHPFC) displays the maximum power density of 137 mW cm−2 and a superior stability. In view of the excellent performance, Pd@N/C foam will be a highly efficient electrode material of DBHPFC.
•A novel Pd decorated 3D porous N/C foam has been successfully prepared.•Pd@N/C-8 foam can be applied to both anode and cathode of DBHPFC.•Pd@N/C-8 foam can effectively improve the fuel utilization.•DBHPFC presents excellent operation stability.
The core@shell structure dimension of the Pd‐based nanocrystals deeply impacts their catalytic properties for C1 and C2 alcohol oxidation reactions. However, the precise simultaneous control on the ...synthesis of core@shell nanocrystals with different shell dimensions is difficult, and most synthesis on Pd‐based core@shell nanocatalysts involves the surfactants participation by multiple steps, thus leads to limited catalytic properties. Herein, for the first time, a facile one‐step surfactant‐free strategy is developed for shell dimension reconstruction of PdAu@Pd core@shell nanocrystals by altering volume ratios of mixed solvents. The Pd‐based sunflower‐like (SL) and coral grass‐like (CGL) nanocrystals are obtained with different 2D hexagonal nanosheet assembles and 3D network shells, respectively. Benefitting from the clean surface shell of 2D ultrathin nanosheets structure, high atom utilization efficiency, and robust electronic effect. The PdAu@Pd SL achieves the ascendant methanol/ethanol/ethylene glycol oxidation reaction (MOR/EOR/EGOR) activities, much higher than Pd/C catalysts, as well as the improved antipoisoning ability. Notably, this one‐step construction shell dimension of PdAu@Pd core@shell catalysts not only provide a significant reference for the improvement of surfactant‐free synthetic routes, but also shed light on the advanced engineering on shell dimensions in core@shell nanostructures for electrocatalysis and so forth.
A facile one‐step and surfactant‐free method is adopted to prepare core@shell PdAu@Pd nanocrystals. The PdAu@Pd with different shell dimensions are precisely reconstructed by altering the ratios of cosolvents. PdAu@Pd SL with 2D hexagonal shell exhibits fast mass transport, high atomic utilization, and optimal geometric effects, which deliver much higher than Pd/C catalysts toward methanol/ethanol/ethylene glycol oxidation reaction (MOR/EOR/EGOR).
•A cocatalyst loading strategy is proposed for wastewater electrochemical treatment.•The cocatalyst NiOOH accelerates the charge transfer, thus promoting water oxidation.•The increased reactive ...oxygen species promote the electrooxidation of organics.•The electrode shows great promise for pharmaceutical wastewater treatment.
Acetaminophen (APAP), a common pharmaceutical and personal care product, is highly toxic and resistant to conventional wastewater treatment. Electrochemical oxidation is a promising technique for removing pharmaceuticals and personal care products (PPCPs), and the Ti-doped α-Fe2O3 electrode is a low-cost alternative to noble-metal electrocatalysts. Herein, we present a novel cocatalyst loading strategy to enhance the electrocatalytic ability of the electrodes by loading a cocatalyst, NiOOH, by electrodeposition. The cocatalyst leads to a higher potential drop (97.7%) on the Helmholtz layer than the bare one (80.5%) and accelerates the charge transfer by ten. The increased production of reactive oxygen species during water activation further facilitates the electrooxidation of APAP, resulting in a threefold increase in removal rate and a twofold increase in Faraday efficiency. Additionally, the obtained NiOOH/Ti-Fe2O3 electrode shows excellent ability (100% APAP removal in 2 h) and stability (removal efficiency greater than 94% after ten cycles) for pharmaceutical wastewater treatment containing APAP. These findings provide a novel and generalized strategy for enhancing the electrocatalytic ability of Ti-doped α-Fe2O3 electrodes and offer valuable guidelines for exploring efficient and economic electrocatalysts for refractory wastewater treatment.
It is a crucial and current challenge to develop efficient metal sulfide bifunctional electrocatalysts for practical applications in direct borohydride-hydrogen peroxide fuel cells (DBHPFCs). In this ...study, a uniform nanoflower-like Ni3S2 is rationally designed and hydrothermally grown on the surface of a 3D nickel foam (NF) support without the need for additional nickel sources, and Pd nanoparticles are further reduced on the surface of nanoflower-like Ni3S2 with sulfur vacancies to form Pd/v-Ni3S2/NF electrode by NaBH4 reduction. The Pd/v-Ni3S2/NF electrode delivers a NaBH4 electrooxidation current density of 902 mA cm−2 at 0.85 V and a H2O2 electroreduction current density of 298 mA cm−2 at 0.65 V in alkaline solutions. Subsequently, Pd/v-Ni3S2/NF electrodes are assembled into DBHPFCs, yielding the optimal power density of 78 mW cm−2 and demonstrating superior long-term stability. These results fully indicate that the nanoflower-like Pd/v-Ni3S2/NF self-supported electrode with abundant sulfur vacancies is a promising bifunctional electrocatalyst for DBHPFCs.
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•Pd/v-Ni3S2/NF was rationally designed by using a simple fabrication process.•Pd/v-Ni3S2/NF electrode delivers a NaBH4 oxidation current density of 902 mA cm−2.•Pd/v-Ni3S2/NF electrode delivers a H2O2 reduction current density of 298 mA cm−2.•Pd/v-Ni3S2/NF was assembled into a DBHFC with higher power density of 78 mW cm−2.•Sulfur vacancy exposed more active sites to achieve super performances.
Rhodium(III) catalysis has enabled a plethora of oxidative C−H functionalizations, which predominantly employ stoichiometric amounts of toxic and/or expensive metal oxidants. In contrast, we herein ...describe the first electrochemical rhodium‐catalyzed C−H activation that avoids hazardous chemical oxidants. Environmentally benign twofold C−H/C−H functionalizations were accomplished with weakly coordinating benzoic acids and benzamides, employing electricity as the terminal oxidant and generating H2 as the sole byproduct.
Elect(Rh)odium: Electrochemical twofold C−H functionalizations of weakly coordinating benzoic acids and benzamides were accomplished by rhodium(III) catalysis with electricity as a sustainable oxidant and the generation of H2 as the sole byproduct.
Alloying Pt electrocatalysts with late transition metals (e.g., Ni, Co, and Fe) is an effective strategy to lower the catalyst cost and improve their tolerance toward CO in the anode of direct ...ethanol fuel cells. In this study, shape-controlled octahedral Pt–Ni/C nanocrystals with uniformly exposed (111) facets and an average edge length of 10 nm were synthesized. The octahedral Pt–Ni/C nanocatalyst was at least 4.6 and 7.7 times more active than conventional Pt–Ni/C and commercial Pt/C catalysts, respectively. In situ infrared spectroscopic results showed that the acetic acid/CO2 absorbance peak intensity on octahedral Pt–Ni/C was 7.6 and 1.4 times higher as compared to commercial Pt/C and conventional Pt–Ni/C, respectively, at 0.75 V. This result suggests that ethanol oxidation on octahedral Pt–Ni produces more acetic acid than on other surfaces. The synergistic electronic and facet effects may explain the superior ethanol oxidation reaction activity of octahedral Pt–Ni/C. Further surface modification with Ru significantly lowered the onset potential for CO2 production by ∼100 mV and resulted in a higher selectivity on CO2 as compared to unmodified surface, which further boosted the ethanol utilization efficiency.
Landfill leachate is a kind of difficult-to-degrade wastewater with complex water qualities. Waste filtrate cannot be thoroughly treated by traditional biological, physical and chemical methods. In ...the past five years, electrochemical methods have attracted widespread attention in the treatment of landfill leachate. The article pointed out that for the colloidal/suspended particles in the landfill leachate, using of electrocoagulation can achieve a good treatment effect. Aiming at the characteristics of the dissolved organic matter in the landfill leachate and the high concentration of chloride ions, a more efficient removal can be available by using of electrooxidation. In this review, the latest achievements and basic principles of electrocoagulation and electrooxidation have been introduced. Meanwhile, the influence of different process parameters on these two electrochemical methods was summarized. It also reviewed the effect of electrochemical technology as an independent system or combined with biological and physical chemical processes on the treatment of landfill leachate, as well as the cost of various laboratory scales. Finally, several main problems and challenges encountered by electrochemical methods were briefly discussed, and the prospects for new development and future research were also provided.
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•Different electrochemical methods for landfill leachate treatment were compared.•Explained the reason of the electrode shape to improve electrocoagulation efficiency•Summarized composite enhanced electrochemical method for landfill leachate treatment.•Prospected the development of electrocoagulation and electrooxidation
