The search for highly efficient and cost-effective electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline electrolytes is essential for the commercial application of anion exchange membrane fuel cells. However, the kinetics of HOR in an alkaline media is much slower than that in an acidic electrolyte, which usually results in orders of magnitude decrease in the catalytic performance. Herein, we report the synthesis of d-p orbital hybridized Ru catalysts through Sn/Ga doping. Density functional theory (DFT) calculations and experimental results including H 2 -temperature programmed desorption (H 2 -TPD) and in situ Raman spectra unveil that the electronic structure modification of Ru derived from the unconventional d-p hybridization could lead to the promoted interfacial water adsorption ability and optimized hydrogen adsorption free energy during the alkaline HOR process. As expected, the d-p hybridized Ru catalyst shows much decreased formation energy of water, which contributes to the changed potential-determining step (PDS) and remarkable HOR activity with the mass activity up to 1790 mA mg Ru −1 . This work not only illustrates the key role of interfacial water adsorption ability but also provides a strategy for rationally designing advanced electrocatalysts for alkaline HOR.
Co-NC catalysts have attracted extensive concerns derived from their high oxygen reduction reaction (ORR) activity, but the catalytic mechanism of Co species with different forms remains controversial. Herein, we prepare Co-NC catalysts with a cobalt nanoparticle-supported and nitrogen-doped carbon structure using the ZIF-67 precursor, in which the Co states in the catalyst present an asymmetric state of an exposed carbon coating (Asy-Co) and a symmetric state of buried carbon (Sy-Co). The acid etching process removed the exposed asymmetric cobalt nanoparticles on the surface. The specific role of cobalt nanoparticles with different forms in the Co-NC catalysts was comprehensively clarified through analyzing the chemical coordination environment by XPS and XAFS. The half-wave potential (E1/2 = 0.83 V) and onset potential (Eon = 1.04 V) of the Co-NC catalysts obtained after acid etching decreased significantly. Thus, the cobalt species removed by the acid etching process offered confirmed contributions to the catalytic activity. This work puts forward an important reference for the design and exploitation of non-noble metal catalysts using symmetry-derived motifs.
The liquid-phase oxidation benzyl alcohol using hydrogen
peroxide
(H2O2) as an oxidant is a promising and green
strategy for manufacturing aldehydes or/and ketones. Herein palladium
(Pd) nanoparticles were impregnated in lumens of halloysite nanotubes
by using ionic liquid (1-(2′-hydroxylethyl)-2,3-dimethylimidazolium
chloride) as directing agents. On the basis of the asymmetric scroll-like
structure of halloysite and the catalytic decomposition ability of
Pd toward H2O2, the prepared catalyst (Pd-IL-HNTs)
exhibited powerful self-propelled movement at an average speed of
276 ± 35 μm/s in 30.0 wt % H2O2 solution.
The specific interaction between nanomotors and benzyl alcohol was
observed as a consequence of self-moving behavior and hydrophobic
interaction introduced by ionic liquid. With the synergistic coupling
of the catalytic ability and powerful movement, Pd-IL-HNTs displayed
outstanding catalytic benzyl alcohol oxidation performance. Compared
to other nonpropelling catalysts using lamellar clay (montmorillonite
and kaolinite) as supports, such HNT-based nanomotors registered superior
catalytic performance, and the TOF value of 118.1 h−1 was obtained.
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