Platinum–Ruthenium Nanotubes and Platinum–Ruthenium Coated Copper Nanowires As Efficient Catalysts for Electro-Oxidation of Methanol

Abstract

The sluggish kinetics of methanol oxidation reaction (MOR) is a major barrier to the commercialization of direct methanol fuel cells (DMFCs). In this work, we report a facile synthesis of platinum–ruthenium nanotubes (PtRuNTs) and platinum–ruthenium-coated copper nanowires (PtRu/CuNWs) by galvanic displacement reaction using copper nanowires as a template. The PtRu compositional effect on MOR is investigated; the optimum Pt/Ru bulk atomic ratio is about 4 and surface atomic ratio about 1 for both PtRuNTs and PtRu/CuNWs. Enhanced specific MOR activities are observed on both PtRuNTs and PtRu/CuNWs compared with the benchmark commercial carbon-supported PtRu catalyst (PtRu/C, Hispec 12100). X-ray photoelectron spectroscopy (XPS) reveals a larger extent of electron transfer from Ru to Pt on PtRu/CuNWs, which may lead to a modification of the d-band center of Pt and consequently a weaker bonding of CO (the poisoning intermediate) on Pt and a higher MOR activity on PtRu/CuNWs.

Mechanistic Insight into the Facet-Dependent Adsorption of Methanol on a Pt3Ni Nanocatalyst

“…However, in practice, DMFCs exhibit low energy density and low efficiency because of the sluggish CH 3 OH oxidation reaction (MOR), which leads to a large overpotential and crossover of methanol from the anode to the cathode. 6,12,13 To lower the anode overpotential, many efforts have been devoted to design and synthesize novel MOR catalysts with different sizes, morphologies, and compositions. 4,6,7,12,14−21 These studies have provided valuable information on the correlation of the catalysts' architecture (such as sizes, morphologies, compositions, and intermetallic structures, etc.)…”

“…However, even with the stateof-art carbon-supported PtRu catalyst, the MOR activity is still not competitive and the anode overpotential of ∼350 mV must be reduced. 6 The MOR is a complex multistep reaction that requires active sites for CH 3 OH adsorption and dehydrogenation as well as sites for supplying oxygen-containing species to the oxidation of the carbonaceous intermediates formed during adsorption and dehydrogenation. 4,13,22,23 For example, the MOR catalyzed by a Pt catalyst can be represented by three main steps.…”

Segregated Pt on Pd nanotubes for enhanced oxygen reduction activity in alkaline electrolyte

“…Furthermore, the high specific activity of the PtPdNTs was achieved without sacrificing mass-normalized activity, which is more than twice that of Pt/C (0.333 A mg PtPdNT À1 vs. 0.141 A mg Pt/C À1 ) and also greater than that of Pd/C (0.221 A mg Pd/C À1 ). [28][29][30][31][32][33][34][35] Notably in the alkaline case, Lima et al demonstrated a volcano-like dependence of ORR specific activity upon the calculated metal d-band center of bulk single-crystal electrodes in alkaline electrolyte, 6 finding optimum activity for Pt monolayers atop Pd(111).In this contribution, we use an accessible and scalable technique to synthesize segregated Pt domains adorning nanotubes of bulk-like, polycrystalline Pd (PtPdNTs). 1,2 Alkaline cells also promise entirely metal-free cathode catalysts, 3 but the production of peroxide on these carbon-based materials may be problematic.…”

“…2,4,5 Metallic catalysts remain the material of choice for the near future of AAEMFCs. [28][29][30][31][32][33][34][35] Notably in the alkaline case, Lima et al demonstrated a volcano-like dependence of ORR specific activity upon the calculated metal d-band center of bulk single-crystal electrodes in alkaline electrolyte, 6 finding optimum activity for Pt monolayers atop Pd(111). 8 The departure from the unsatisfactory performance of Pd in acid is owed to subtle changes with respect to reactant/product binding energy, 9 pH-dependent coverage of oxides and spectator species, 6,10,11 and the role of water as catalytic promoter.…”

“…12 Research into the ORR in both acidic and alkaline electrolyte has yielded a blueprint for tuning the reactant/product binding strength for the development of highly active catalysts. [28][29][30][31][32][33][34][35] Notably in the alkaline case, Lima et al demonstrated a volcano-like dependence of ORR specific activity upon the calculated metal d-band center of bulk single-crystal electrodes in alkaline electrolyte, 6 finding optimum activity for Pt monolayers atop Pd(111). [28][29][30][31][32][33][34][35] Notably in the alkaline case, Lima et al demonstrated a volcano-like dependence of ORR specific activity upon the calculated metal d-band center of bulk single-crystal electrodes in alkaline electrolyte, 6 finding optimum activity for Pt monolayers atop Pd(111).…”