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H2 Reduction Annealing Induced Phase Transition and Improvements on Redox Durability of Pt Cluster-Decorated Cu@Pd Electrocatalysts in Oxygen Reduction Reaction
journal contribution
posted on 2019-01-11, 09:14 authored by Dinesh Bhalothia, Cheng-Yang Lin, Che Yan, Ya-Tang Yang, Tsan-Yao ChenHierarchical
structures in shell with transition metal underneath
is a promising design for high-performance and low-cost heterogeneous
nanocatalysts (NCs). Such a design enables the optimum extent of synergetic
effects in NC surface. It facilitates intermediate reaction steps
and, therefore, boosts activity of NC in oxygen reduction reaction
(ORR). In this study, carbon nanotube (CNT)-supported ternary metallic
NC comprising Cucluster-in-Pdcluster nanocrystal
and surface decoration of atomic Pt clusters (14 wt %) is synthesized
by using the wet chemical reduction method with sequence and reaction
time controls. By annealing in H2 environment (H2/N2 = 9:1, 10 sccm) at 600 K for 2 h, specific activity
of Cu@Pd/Pt is substantially improved by ∼2.0-fold as compared
to that of the pristine sample and commercial Pt catalysts. By cross-referencing
results of electron microscopic, X-ray spectroscopic, and electrochemical
analyses, we demonstrated that reduction annealing turns ternary NC
into complex of Cu3Pt alloy and CuxPd1–x alloy. Such a transition
preserves Pt and Pd in metallic phases, therefore improving the activity
by ∼29% and the stability of NC in an accelerated degradation
test (ADT) as compared to those of pristine Cu@Pd/Pt in 36 000
cycles at 0.85 V (vs RHE). This study presents robust H2 annealing for structure stabilization of NC and systematic characterizations
for rationalization of the corresponding mechanisms. These results
provide promising scenarios for facilitation of heterogeneous NC in
ORR applications.
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Keywords
Oxygen Reduction Reaction Hierarchical structuresH 2 environmentboosts activityORR applicationsCu cluster36 000X-ray spectroscopich 2 Reduction Annealing Induced Phase Transitionsynergetic effectssurface decorationvs RHEcarbon nanotubeNC surfacereaction time controlsreduction annealingreaction steps36 000 cycleselectrochemical analysesoxygen reduction reactionstructure stabilizationcross-referencing resultstransition metalternary NCCu 3 Pt alloy600 Kin-Pd cluster nanocrystalADTRedox Durabilitychemical reduction methoddegradation test2 hH 2 annealingCNTPt catalysts0.85 V
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