PtRu/Ti anodes with varying Pt ? Ru ratio prepared by electrodeposition for the direct methanol fuel cell

Comparative DFT study of methanol decomposition on Mo2C(001) and Mo2C(101) surfaces

CONTEXT

In this study, the complete reaction mechanism of methanol decomposition on metallic Mo₂C(001) and Mo/C-mixed Mo₂C(101) hexagonal Mo₂C crystalline phases was systematically investigated using plane-wave-based periodic density functional theory (DFT). The main reaction route for Mo₂C(001) is as follows: CH₃OH → CH₃O + H → CH₂O + 2H → CHO + 3H → CO + 4H → C + O + 4H. Hence, C, O, and H are the main products. It was found that the energy barrier for CO dissociation was low. Therefore, it was concluded that the Mo₂C(001) surface was too active to be easily oxidized or carburized. The optimal reaction pathway for Mo₂C(101) is as follows: CH₃OH → CH₃O + H → CH₂O + 2H → CH₂ + O + 2H → CH₃ + O + H → CH₄ + O. Therefore, CH₄ is the major product. The hydrogenation of CH₃ leading to CH₄ showed the highest energy barrier and the lowest rate constant and should be the rate-determining step. In addition, the formation of CO + 2H₂ was competitive on Mo₂C(101), and the optimal path was CH₃OH → CH₃O + H → CH₂O + 2H → CH₂ + O + 2H → CH + O + 3H → C + O + 4H → CO + 2H₂. The computed energy barrier and rate constant indicate that the rate-determining step is the last step in CO formation. In agreement with the experimental observations, the results provide insights into the Mo₂C-catalyzed decomposition of methanol and other side reactions.

METHODS

All calculations were performed by using the plane-wave based periodic method implemented in Vienna ab initio simulation package (VASP, version 5.3.5), where the ionic cores are described by the projector augmented wave (PAW) method. The exchange and correlation energies were computed using the Perdew, Burke and Ernzerhof functional with the latest dispersion correction (PBE-D3).

Rapid synthesis of a PtRu nano-sponge with different surface compositions and performance evaluation for methanol electrooxidation

A rapid strategy to synthesize a highly active PtRu alloy nano-sponge catalyst system for methanol electro-oxidation is presented. The greatly increased Pt utilization, anti-CO poisoning ability and electronic effect resulting from the porous nano-sponge structure could account for the performance improvement.

Methanol electro-oxidation on platinum modified tungsten carbides in direct methanol fuel cells: a DFT study

Bilayer Pt-modified WC catalysts exhibit up to 2.4 times higher MOR reactivity compared to that of pure Pt.

The origin of high activity but low CO2 selectivity on binary PtSn in the direct ethanol fuel cell

Combined electrochemical in situ FTIR and DFT study provides an insight into ethanol fuel cell catalysis on the most active binary catalyst, PtSn, at the atomic and molecular levels.

Direct Methanol Fuel Cell – Alternative Materials and Catalyst Preparation

The direct methanol fuel cell is the most interesting fuel cell for mobile applications. The state-of-the-art materials in a practical direct methanol fuel cell are Nafion 115 as membrane, carbon black as catalyst support and PtRu and Pt, respectively, as electrocatalyst. However, many materials were under investigation as alternatives to these materials in the last two decades. The most promising materials are reviewed in this paper. In addition, the catalyst preparation methods are summarized for chemical and electrochemical methods separately. Furthermore, a new electrodeposition technique with a gel-type electrolyte is highlighted. By the use of this method, the catalyst loading on the cathode side can be reduced by 25%.

Nanoporous PtRu alloys for electrocatalysis

We describe a facile route to the straightforward fabrication of nanoporous (NP) PtRu alloys with predetermined bimetallic compositions. Electron microscopy and X-ray diffraction characterizations demonstrate that selective etching of Al from ternary PtRuAl source alloys generates three-dimensional bicontinuous NP-PtRu alloy nanostructures with a single-phase face-centered-cubic crystalline structure. X-ray photoelectron spectroscopy shows a slight electronic structure modification of Pt by alloying with Ru as well as uniform surface and bulk bimetallic ratio. With characteristic structural dimensions less than 5 nm, these high surface area bimetallic nanostructures show distinct electrocatalytic performance as the Ru content varies within the structure. Among all samples, NP-Pt(70)Ru(30) shows the highest specific activity as well as the most negative onset potential toward methanol oxidation reaction. NP-Pt(50)Ru(50) was found to possess a similar specific activity to the commercial E-TEK Pt(50)Ru(50)/C catalyst, but its onset and peak potentials are about 70 mV more negative. CO stripping experiments demonstrate that the adsorption of CO is the weakest on NP-Pt(70)Ru(30), and further increasing the Ru content actually shifts the CO stripping peak to a more positive potential. Thus, the overall sequence for CO-tolerance is NP-Pt(70)Ru(30) > NP-Pt(50)Ru(50) approximately = Pt(50)Ru(50)/C > NP-Pt(30)Ru(70) > Pt/C.