Abstract
Electrochemical deposition is a viable approach to develop novel catalyst structures, such as Pt thin films on conductive support materials. Most studies, reaching out to control electrochemical deposition of Pt to monolayer quantities focus on noble metal substrates (e.g., Au). In contrast, conductive oxides, such as antimony doped tin oxide (ATO), are considered as support material for different applications, e.g., as fuel cell catalysts. Herein, we investigate the deposition process of Pt on Sn, used as a model system for the electrochemical deposition of Pt on non-noble metal oxide supports. Doing so, we shade some light on the differences of a metallic Sn surface and surface oxide species in electrochemical deposition processes. With respect to a borate buffer solution, containing K2PtCl4 as Pt precursor, we report for the first time that surface oxides have the capability to fully inhibit the electrochemical deposition of Pt. Furthermore, direct alloying of the deposited Pt with the Sn support during the electrodeposition process yielded a catalyst with a high activity for the oxidation of CO.
Highlights
Fuel cells are considered as a candidate to replace the currently wide-spread combustion engine and limit the exhaust of CO2, e.g., caused by automotive traffic
Most electrochemical deposition techniques, aiming to achieve low loading Pt deposits focus on noble metal substrates, whereas deposition of low platinum quantities on non-noble metals or conductive oxides was only scarcely reported[13]
According to the results presented here, we propose that oxide species on the surface of Pt and Sn electrodes are capable of fully inhibiting Pt deposition under the conditions applied here, even though high cathodic overpotentials are applied to the system
Summary
Fuel cells are considered as a candidate to replace the currently wide-spread combustion engine and limit the exhaust of CO2, e.g., caused by automotive traffic. There is a demand for novel electrocatalysts due to the low abundance of Pt and the limited stability of current catalysts under fuel cell operating conditions[4] In this respect, film-like structures on non-noble metal based supports, such as antimony doped tin oxide (ATO), are of potential interest due to various reasons. The scanning tunneling microscopy (STM) images of the resulting deposits showed an island-like morphology of very small Pt deposits on the Au surface Similar to those studies, most electrochemical deposition techniques, aiming to achieve low loading Pt deposits focus on noble metal substrates, whereas deposition of low platinum quantities on non-noble metals or conductive oxides was only scarcely reported (e.g., on Ni)[13]. We are able to identify the deposits as PtSn alloys, formed directly on the surface of the electrode during the deposition process
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