Search

The two‐electron pathway to form hydrogen peroxide (H2O2) is undesirable for the oxygen reduction reaction (ORR) in iron and nitrogen doped carbon (Fe–N–C) material as it not only lowers the catalytic efficiency but also impairs the catalyst durability. In this study, a relay catalysis pathway is designed to minimize the two‐electron selectivity of Fe–N–C catalyst. Such a design is achieved by introducing two other sites, that is, MnN4 site and α‐Fe(110) face. A combination of transmission electron microscopy image and X‐ray absorption spectra verify the three site formation. Electrochemical test coupled with post‐treatment confirm the improvement of MnN4 site and α‐Fe(110) face on catalyst performance. Theoretical calculation proposes a relay catalysis pathway of three sites, that is, H2O2 released from the FeN4 site migrates to the MnN4 site or α‐Fe(110) face, on which the captive H2O2 is further reduced to H2O. The relay catalysis pathway positioned the as‐prepared catalyst among the best ORR catalysts in both aqueous electrode and alkaline direct methanol fuel cell test. This study examples an interesting relay catalysis pathway of multi‐sites for the ORR, which offers insights into the design of efficient electrocatalysts for fuel cells or beyond. [ABSTRACT FROM AUTHOR]

The preparation of metal electrocatalysts with excellent comprehensive properties for application in alcohol fuel cells is an urgent issue. This study reports a novel 3D Au‐doped PtBi intermetallic phase woven by sub‐7 nm building blocks. The high‐efficiency "active auxiliary" Au advances the activity and in situ anti‐CO poisoning upon ethylene glycol electrooxidation on 3D PtBiAu, along with high CC bond cleavage and attainment of a ten‐electron complete electrooxidation via a CO‐free pathway. The interface‐rich 3D structure with "nanocontainer" function, electronic effect, and dual functional sites of "Pt–Au" or "Pt–Bi" enable the 3D PtBiAu to outperform industrial Pt black and 3D PtBi intermetallics significantly. The mass activity on the 3D Pt53.1Bi43.4Au3.5 intermetallics boosts to 28.72 A mgPt−1, higher than that reported in a previous study. The 3D Pt53.1Bi43.4Au3.5 exhibits superior performance to industrial Pt/C in direct ethylene glycol fuel cells (DEGFCs). The peak power density of 3D Pt53.1Bi43.4Au3.5 is 145/92 mW cm−2 in O2/air (80 °C). Importantly, the cell voltage shows a negligible decay in both O2 and air during the 20 h durability testing. This study results in the development of novel 3D PtBiAu intermetallics as high‐performance anode electrocatalysts for application in DEGFCs. [ABSTRACT FROM AUTHOR]

An Fe/N/C catalyst derived from the pyrolysis of metal–organic frameworks, for example, a zeolitic‐imidazolate‐framework‐8 (ZIF‐8), has been regarded as one of the most promising non‐precious metal catalysts toward oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, its ORR mass activity is still much inferior to that of Pt, partly because of the lack of general and efficient synthetic strategies. Herein, a general carboxylate‐assisted strategy that dramatically enhances the ORR mass activity of ZIF‐derived Fe/N/C catalysts is reported. The carboxylate is found to promote the formation of Fe/N/C catalysts with denser accessible active sites and entangled carbon nanotubes, as well as a higher mesoporosity. These structural advantages make the carboxylate‐assisted Fe/N/C catalysts show a 2–10 fold higher ORR mass activity than the common carboxylate‐free one in various cases. When applied in H2–O2 PEMFCs, the active acetate‐assisted Fe/N/C catalyst generates a peak power density of 1.33 W cm−2, a new record of peak power density for a H2–O2 PEMFC with non‐Pt ORR catalysts. [ABSTRACT FROM AUTHOR]

Recently, in order to improve the energy conversion efficiency of direct polyol fuel cells, the engineering of effective Pd‐ and/or Pt‐based electrocatalysts to rupture CC bonds has received increasing attention. Here, an example is shown to synthesize highly uniform sub‐10 nm Pd‐Cu‐Pt twin icosahedrons by controlling the nucleation phase. Because of the synergies of the electronic effect, synergistic effect, geometric effect, and abundant surface active sites originating from the formation of near surface alloy and special icosahedral shape, the Pd‐Cu‐Pt twin icosahedrons exhibit excellent electrocatalytic performance in glycerol electrocatalysis at the operating temperature of direct alcohol fuel cells (70 °C) in KOH electrolyte. The Pd50.2Cu38.4Pt11.4 icosahedrons show mass activities of 9.7 A mg−1Pd+Pt and 13.7 A mg−1Pd. Furthermore, the Pd50.2Cu38.4Pt11.4 icosahedrons demonstrate long‐term durability in current–time test for 36 000 s and high in situ anti‐CO poisoning performance. In addition, the introduction of CO can enhance electro‐oxidation endurance on Pd50.2Cu38.4Pt11.4 icosahedrons, and the peak mass activity can reach to 14.4 A mg−1Pd+Pt. The in situ Fourier transform infrared spectroscopy spectra indicate that the Pd50.2Cu38.4Pt11.4 icosahedrons possess a high capacity to break CC bonds and may efficiently convert glycerol into CO2, thus improving the utilization efficiency of energy‐containing molecule glycerol. [ABSTRACT FROM AUTHOR]

Grain boundary enriched CuO nanobundle was reported to significantly increased the glucose diffusion as well as reduce the glucose oxidation barrier, thus displayed a lower onset potential of 94 mV, an extremely high sensitivity of 7474 μA mM−1 cm−2 in glucose detection and a high peak power density of 242 W m−2 in a glucose fuel cell. [Display omitted] • CuO nanobundle with high density and homogenous GBs was obtained by a facile and large-scale method. • A high sensitivity of 7474 μA mM−1 cm−2 in glucose detection and a high peak power density of 242 W m−2 in a glucose fuel cell are achieved. • CuO-NB possesses the faster glucose mass transfer due to the terraces in GBs dislocation surface. • Electrons accumulate on GBs interfaces promote glucose adsorption and decrease free energy of dehydrogenation step. Glucose oxidation reaction (GOR) plays a significant role in glucose fuel cells anode and glucose sensors. Therefore, optimizing the GOR catalyst nanostructure is auxiliary to their efficient operation. In this study, we present a cascade-assembled strategy to prepare CuO nanobundles (CuO-NB) with high-density and homogenous grain boundaries (GBs). The essence of activity in GOR that depended on GBs are thoroughly investigated. The increased glucose diffusion coefficient of CuO-NB means that GBs has a faster glucose mass transfer, which is attributed to the terraces in GBs dislocation surface. Furthermore, the accumulation of electrons on GBs makes the glucose adsorption increased and the free energy of dehydrogenation step decreased, leading to a lower glucose oxidation barrier. Therefore, CuO-NB is appropriate for non-invasive glucose detection and glucose fuel cells. This study sheds new light on the GBs effect in GOR and paves the way for developing high-efficiency electrocatalysts. [ABSTRACT FROM AUTHOR]

• A KOH-doped PBI membrane was applied in DHFC for the first time. • The influence of anolyte, membrane thickness and oxygen humidity was investigated. • A peak power density of 0.708 W cm−2 was achieved. Alkaline direct hydrazine (N 2 H 4) fuel cells (DHFCs) are considered one of the most promising liquid-fed fuel cells because of their high energy density, high theoretical voltage, and zero carbon dioxide (CO 2) emissions. However, the lack of a suitable electrolyte membrane impedes the further development of alkaline DHFC. Herein, a potassium hydroxide (KOH)-doped polybenzimidazole (PBI) membrane is applied in alkaline DHFCs, and the detailed operating conditions are investigated for the first time. With optimal KOH and N 2 H 4 concentrations in the anolyte, membrane thickness, and cathode gas humidity, the DHFC gives a peak power density of 0.708 W cm−2. The results of this study demonstrate the promising application of PBI membranes in DHFC and provide a platform to evaluate the performance of catalysts synthesized for DHFC. [ABSTRACT FROM AUTHOR]

PtCu hollow octahedral nanoparticles with wall thickness of ~2.1 nm have been successfully achieved to be as efficient bifunctional electrocatalysts toward oxygen reduction reaction and methanol oxidation reaction. • PtCu hollow octahedrons (HOs) with wall thickness of ~2.1 nm have been achieved. • The MA of PtCu/C HOs toward ORR boosts to 2.60 A mg Pt -1. • After 10,000 voltage cycles, the MA of Pt 44.1 Cu 55.9 /C HONs remains 1.63 A mg Pt -1. • The optimum MA of methanol electrooxidation on PtCu/C HONs is 1.94 A mg Pt -1. In response to the scarcity of precious metals, the development of precious-metal-saving electrocatalysts exhibiting high mass activity (MA) and durability towards oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) for both proton-exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) has aroused increasing attention. In this study, octahedral Cu-rich PtCu alloy is seeded to fabricate near-surface composition-tunable PtCu hollow octahedral nanoparticles (HONs) with the wall thickness of ~2.1 nm. Due to both the alloying effects of near surface and the special hollow octahedral structure, the PtCu/C HONs exhibit significantly higher MA and durability than commercial Pt/C towards both ORR in alkaline medium and MOR in sulfuric acid electrolyte. The ORR MA of Pt 44.1 Cu 55.9 /C HONs are up to 2.60 A mg Pt −1 that is 18.5-fold enhancement compared with that of Pt/C. Besides, after 10,000 voltage cycles, the MA of Pt 44.1 Cu 55.9 /C HONs remains to be 1.61 A mg Pt −1, a datum 53.7 times that of Pt/C. The in situ CO polarization curves exhibit that the Pt 44.1 Cu 55.9 HONs/C own high resistance to CO poisoning. For MOR in sulfuric acid electrolyte, the optimum SA/MA of PtCu/C HONs is 5.33 mA cm−2/1.94 A mg Pt −1, which is 10.25/5.87 times higher than that of Pt/C. This study provides effective bifunctional cathode and anode electrocatalysts for both PEMFCs and DMFCs. [ABSTRACT FROM AUTHOR]