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. 2015 Nov 25:6:10035.
doi: 10.1038/ncomms10035.

Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene

Wenjing Huang  1 , Hongtao Wang  2 , Jigang Zhou  3 , Jian Wang  3 , Paul N Duchesne  4 , David Muir  3 , Peng Zhang  4 , Na Han  1 , Feipeng Zhao  1 , Min Zeng  1 , Jun Zhong  1 , Chuanhong Jin  2 , Yanguang Li  1 , Shuit-Tong Lee  1 , Hongjie Dai  5
Affiliations

Highly active and durable methanol oxidation electrocatalyst based on the synergy of platinum-nickel hydroxide-graphene

Wenjing Huang et al. Nat Commun. .

Abstract

Active and durable electrocatalysts for methanol oxidation reaction are of critical importance to the commercial viability of direct methanol fuel cell technology. Unfortunately, current methanol oxidation electrocatalysts fall far short of expectations and suffer from rapid activity degradation. Here we report platinum-nickel hydroxide-graphene ternary hybrids as a possible solution to this long-standing issue. The incorporation of highly defective nickel hydroxide nanostructures is believed to play the decisive role in promoting the dissociative adsorption of water molecules and subsequent oxidative removal of carbonaceous poison on neighbouring platinum sites. As a result, the ternary hybrids exhibit exceptional activity and durability towards efficient methanol oxidation reaction. Under periodic reactivations, the hybrids can endure at least 500,000 s with negligible activity loss, which is, to the best of our knowledge, two to three orders of magnitude longer than all available electrocatalysts.

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Figures

Figure 1
Figure 1. Preparation and microscopic characterizations of Pt/Ni(OH)2/rGO ternary hybrids.
(a) A schematic illustration of the two-step solution method to prepare the ternary hybrid materials. Representative (b) SEM, (c,d) TEM and (e) annual dark-field image under STEM (STEM-ADF) images of Pt/Ni(OH)2/rGO-4. Representative (f) STEM image and its corresponding (g) Pt EDS mapping, (h) Ni EDS mapping and (i) combined Pt and Ni mapping of Pt/Ni(OH)2/rGO-4. Microscopic characterization results suggest that small-sized Pt nanocrystals are adequately interfaced with defective Ni(OH)2 and supported on rGO nanosheets. Scale bars, 100 nm (b), 20 nm (c), 2 nm (d–e) and 4 nm (f–i).
Figure 2
Figure 2. X-ray absorption spectroscopic characterizations of Pt/Ni(OH)2/rGO ternary hybrids.
(a) C K-edge XANES spectrum of Pt/Ni(OH)2/rGO-4 in comparison with Ni(OH)2/rGO and rGO. (b) Pt L3-edge XANES spectrum of Pt/Ni(OH)2/rGO-4 in comparison with standard Pt foil. (c) Fourier transform EXAFS spectrum of Pt/Ni(OH)2/rGO-4 and associated fitting curve at the Pt L3-edge. (d) Representative scanning transmission X-ray microscopy mapping of Ni L3,2-edge intensity (red) over one rGO nanosheet suspended on lacy carbon support (green). Scale bar, 2 μm (d). XAS data suggest strong mutual interactions between the three components in the hybrid materials.
Figure 3
Figure 3. Electrochemical performance of Pt/Ni(OH)2/rGO ternary hybrids for MOR electrocatalysis.
(a) CV curve of Pt/Ni(OH)2/rGO-4 in 1 M KOH. (b) CV curves of Pt/Ni(OH)2/rGO-4, Pt/rGO hybrid and standard 20 wt% Pt/C in 1 M methanol/1 M KOH. (c) Short-term durability measurement of Pt/Ni(OH)2/rGO-4 at −0.30 V versus SCE in 1 M methanol/1 M KOH in comparison with Pt/rGO, standard 20 wt% Pt/C and 20 wt% PtRu/C. (d–g) Long-term durability measurements of (d) standard 20 wt% Pt/C, (e) standard 20 wt% PtRu/C, (f) Pt/rGO and (g) Pt/Ni(OH)2/rGO-4. The dash lines indicate when electrocatalysts were reactivated in clean KOH. In b–g, current densities are normalized to the mass of precious metals (Pt or Ru) in the working electrode. These electrochemical data suggest high MOR activity and unprecedented durability of Pt/Ni(OH)2/rGO hybrids.
Figure 4
Figure 4. The critical role of defective Ni(OH)2 to the exceptional MOR performance of ternary hybrids.
(a) A schematic illustration showing the bifunctional interaction between Ni(OH)2 and adjacent Pt sites for the dissociate adsorption of water molecules and subsequently the oxidative removal of CO on Pt sites via the L–H pathway. CO stripping experiments of (b) standard 20 wt% Pt/C, (c) standard 20 wt% PtRu/C, (d) Pt/rGO and (e) Pt/Ni(OH)2/rGO-4 in 1 M KOH. (f–i) Response of (f) standard 20 wt% Pt/C, (g) standard 20 wt% PtRu/C, (h) Pt/rGO and (i) Pt/Ni(OH)2/rGO-4 to intentional CO poisoning in 1 M methanol/1 M KOH. During the chronoamperometric measurements at −0.3 V, 10% CO/N2 gas was bubbled to the electrolyte at where arrows indicate. The incorporation of defective Ni(OH)2 enables high CO resistance and superb MOR performance of ternary hybrids.
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