Ternary electrocatalysts

Comparison with Model Calculations of CO Tolerance of Ternary Electrocatalysts... 

A large screening was recently done to identify such a third metal, X, to add to platinum and ruthenium [52]. Figure 5 summarizes the behavior of the nine investigated Pt-Ru-X trimetallic electrocatalysts toward methanol oxidation. At low potentials, the Pt-Ru-Mo ternary catalyst gives the highest current densities compared to other ternary electrocatalysts. This catalyst exhibits a current density 10 times greater than Pt-Ru at a potential of 400 mV versus RHF under steady-state conditions (data taken after 5 minutes). 

Ternary Electrocatalysts for Oxidizing Ethanol to Carbon Dioxide... 

Li M, Cullen D, Sasaki K, Marinkovic NS, More K, Adzic RR (2013) Ternary electrocatalysts for oxidizing ethanol to carbon dioxide making Ir capable of splitting C-C bond. J Am Chem Soc 135 132-141... 

Wang RF, Liao SJ, Fu ZY, Ji S (2008) Platinum free ternary electrocatalysts prepared via organic colloidal method for oxygen reduction. Electrochem Commun 10(4) 523-526... 

Na2Si03, Na4Si20s, gas phase reduction [11,15,19,21]. Generally, metal chloride salts (H2PtCl6, RuCls, NiCU, etc.) are used as metal precursors. As metal chloride salts may reduce the dispersion of nanoparticles (NPs) on support materials [21], a number of binary and ternary electrocatalysts have also been prepared by using chloride-free precursor salts such as carbonyl, nitrate, sulfite complexes, etc. [15,21]. NaBH4 and polyol reduction methods are repeatedly used [15,21-25]. Recently, the microwave assisted chemical reduction method has also been used to obtain better dispersion and reduce the particle sizes of metal catalysts [24-26]. 

Lee K, Zhang L, Zhang J (2007) Ternary non-noble mefal chalcogenide (W-Co-Se) as electrocatalyst for oxygen reduction reaction. Electrochem Commun 9 1704-1708... 

This chapter presents the design and application of a two-stage combinatorial and high-throughput screening electrochemical workflow for the development of new fuel cell electrocatalysts. First, a brief description of combinatorial methodologies in electrocatalysis is presented. Then, the primary and secondary electrochemical workflows are described in detail. Finally, a case study on ternary methanol oxidation catalysts for DMFC anodes illustrates the application of the workflow to fuel cell research. 

Over the past 35 years, much has been learned about the electrooxidation of methanol on the surface of noble metals and metal alloys, in particular platinum and ruthenium [2, 4, 6, 7]. Significant overpotential losses occur in the reaction due to poisoning of the alloy catalyst surface by carbon monoxide. Yet, Pt-based metal alloys are still the most popular catalyst materials in the development of new fuel cell electrocatalysts, based on the expectation that a more CO-tolerant methanol catalyst will be developed. The vast ternary composition space beyond Pt-Ru catalysts has not been adequately explored. This section demonstrates how the ternary space can be explored using the high-throughput, electrocatalyst workflow described above. 

Fig. 11.10 Parallel chronoamperometric screening of a 64-element, thin film electrocatalyst library for the oxidation of methanol. The library contained a diverse set of binary, ternary and quaternary electrocatalyst compositions consisting of Pt in combination with W, Ni, Co and Ru. The graph plots current vs. time and channel number. Conditions 1 M methanol, 0.5 M H2S04, room temperature, = + 450 mV/RHE, test time = 5 min. For clarity, channel numbers 2-4,10,12,19, 20, 23, 26-29, 42,45 and 57 are omitted. (Reproduced from [18]).

In conclusion, the computational study of ternary Pt-Ru-X alloys suggests that future strategies toward more active electrocatalysts for the oxidation of methanol should be based on a modification of the CO adsorption energy of Pt (ligand effect), rather than on the enhancement of the oxophilic properties of alloy components (enhanced bifunctional effect). 

Fig. 11.15 Design of an electrocatalyst library of Pt-Ru-Co alloys for a more focused examination of the ternary com position space. The pie-chart character of each catalyst represents its chemical composition, with pure Pt in the upper left corner. The design was created using Library Studio [31],...

Fig. 11.13 Stability analysis of the most active ternary composition, Pt14Co63Ru23, shown in Fig. 11.17. (a) Location of the electrocatalyst within the ternary composition map. (b) Comparison of the XRD profile of the electrocatalyst before and after screening. The dominant diffraction peak shifts slightly to larger lattice parameters, indicating leaching of cobalt. Significant intensity degradation (relative to the Ti electrode) has occurred after screening. Diffraction of a bare Ti electrode is shown for comparison.

Strasser, P., Fan, Q., Devenney, M., Weinberg, W. H., Combinatorial Exploration of ternary fuel cell electrocatalysts for DMFC anodes — a comparative study of PtRuCo, PtRuNi and PtRuW systems, AIChE fall meeting, 2003, San Francisco. 

The SECM capacity for rapid screening of an array of catalyst spots makes it a valuable tool for studies of electrocatalysts. This technique was used to screen the arrays of bimetallic or trimetallic catalyst spots with different compositions on a GC support in search of inexpensive and efficient electrocatalytic materials for polymer electrolyte membrane fuel cells (PEMFC) [126]. Each spot contained some binary or ternary combination of Pd, Au, Ag, and Co deposited on a glassy carbon substrate. The electrocatalytic activity of these materials for the ORR in acidic media (0.5 M H2S04) was examined using SECM in a rapidimaging mode. The SECM tip was scanned in the x—y plane over the substrate surface while electrogenerating 02 from H20 at constant current. By scanning... 

Mani P, Srivastava R, Strasser P. Dealloyed binary PtM3 (M = Cu, Co, Ni) and ternary PtNbM (M = Cu, Co, Fe, Cr) electrocatalysts for the oxygen reduction reaction performance in polymer electrolyte membrane fuel cells. J Power Sources. 2011 196 666-73. 

It became obvious that long-term stability of high surface area electrocatalysts was as important, or even more important than short-term activity. Luczak36 and Landsman pioneered the heat treatment of ternary alloy electrocatalysts in order to provide an ordered crystallite structure. This work was followed in Japan by Itoh and Katoh, and subsequently by... 

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