Pt Alloy and Intermetallic Phases with V, Cr, Mn, Ni, and Cu: Synthesis As Nanomaterials and Possible Applications As Fuel Cell Catalysts

Abstract

Nanomaterials as catalysts for fuel cells are not only highly desirable, but necessary to reach the high reaction rates (or power densities) demanded by many applications. The exploration of catalyst materials beyond Pt metal, such as Pt containing alloys and intermetallics, immediately leads to significant synthetic challenges to prepare nanoparticles with controlled composition, structure, and morphology. To facilitate a comprehensive study of these materials, a generalized synthetic approach is desirable. This requires an in-depth understanding and control of relevant factors that thermodynamically and kinetically define the synthesis process. Once synthesized, electrochemical activities of these materials can then be studied to aid in designing the next steps in further optimizing the catalyst activity. In this work, we have been able to demonstrate synthesis of several phases (both alloy and ordered intermetallics for binary Pt−V/Mn/Cr/Ni/Cu systems) that rarely, if ever, have been synthesized as nanomaterials without using surfactants. Additionally, we have shown that some of these materials are active catalysts, with activity superior to Pt for formic acid oxidation. Finally, we have established general guidelines and methodologies for synthesis of alloy and intermetallic phases as nanomaterials with highly reactive metals like Cr, V, and Mn.

Intermetallic Nanocrystals: Syntheses and Catalytic Applications

“…In addition, different from random alloys, ordered intermetallic nanocrystals offer predictable control over structural, geometric, electronic, and ensemble effects. The last two decades have witnessed the successful synthesis of Pt‐based intermetallic nanocrystals through the incorporation of oxyphilic metals such as Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Ag, Zn, In, Sn, Pb, Sb, and Bi, toward the oxidation of fuel with enhanced catalytic properties …”

The Oxygen Reduction Activity of Pt-Mn/C and Pt-Cu/C Alloys

“…Pt is the most commonly used electrocatalyst for both cathodic and anodic reaction in the commercial fuel cells. Pt is an expensive element and the efforts to reduce Pt and other noble metal contents in fuel cells are challenging [11][12][13][14]. On the other hand, the new non-noble metal catalysts have shown a low mass activity in fuel cells [3,15,16].…”

Ordered intermediate compound PtBi-modified Pt/C catalyst for 2-propanol electrooxidation in alkaline medium

“…Intermetallic compounds, which are atomically ordered alloys that tend to have well-defined compositions and crystal structures that differ from those of their constituent elements, have been used as catalysts for quite some time for chemical transformations such as hydrogenation, ammonia synthesis, methanol synthesis and methanol oxidation [19]. In particular, recent work has shown that intermetallic alloys are potential candidates for catalysis in the electrochemical oxidation of small organic molecules (SOMs) because of their increased current densities and their improved resistance to CO poisoning [20][21][22][23]. Roychowdhury et al [24] prepared the ordered intermetallic compounds PtBi and PtPb using anhydrous methanol as the solvent and sodium borohydride as the reducing agent.…”

“…Recently, Miura et al [28] synthesized the intermetallic PtZn nanoparticles with stable and high activities toward formic acid and methanol electrooxidation. Ghosh et al [22] have been able to demonstrate synthesis of several phases (both alloy and ordered intermetallics for binary Pt-V/Mn/Cr/Ni/Cu systems) that rarely, if ever, have been synthesized as nanomaterials without using surfactants. Additionally, they have shown that some of these materials are active catalysts, with activity superior to Pt for formic acid oxidation.…”