In this work, doped nanocarbon electrocatalysts for electrochemical oxygen reduction reaction (ORR) are prepared by high-temperature pyrolysis from Honeyol, cobalt and iron salts, and dicyandiamide. MgO-based inorganic templates are further used to increase the mesoporosity of the prepared catalyst materials. The templated bimetallic electrocatalyst containing iron and cobalt (FeCoNC-MgOAc) showed excellent stability and remarkable ORR performance in rotating disk electrode testing in alkaline conditions. The catalyst was further tested in anion-exchange membrane fuel cells (AEMFCs), where FeCoNC-MgOAc performed significantly better than the nontemplated material (FeCoNC), yielding a peak power density (P max ) of 0.92 W cm −2 surpassing that of the commercial Pt/C (20 and 40 wt %) catalysts (P max = 0.85 and 0.69 W cm −2 , respectively). The high AEMFC performance was attributed to the mesoporous morphology and high density of active sites in the nanocarbon-based cathode catalyst.
Thin HfO2 films were grown by atomic layer deposition
on chemical vapor-deposited large-area graphene. The graphene was
transferred, prior to the deposition of the HfO2 overlayer,
to the HfO2 bottom dielectric layer pregrown on the Si/TiN
substrate. Either HfCl4 or Hf[N(CH3)(C2H5)]4 was used as the metal precursor for the
bottom layer. The O2 plasma-assisted process was applied
for growing HfO2 from Hf[N(CH3)(C2H5)]4 also on the top of graphene. To improve
graphene transfer, the effects of the surface pretreatments of the
as-grown and aged Si/TiN/HfO2 substrates were studied and
compared. The graphene layer retained its integrity after the plasma
processes. Studies on resistive switching on HfO2-graphene-HfO2 nanostructures revealed that the operational voltage ranges
in the graphene-HfO2 stacks were modified together with
the ratios between high- and low-resistance states.
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