| Surface deposition processes of metal adatoms on metal substrates have received widespread attention during the past few decades due to the importance of bimetallic systems in heterogeneous catalysis. Noble metal catalysts, in particular, can be successfully modified by another metal to create bimetallic systems that exhibit higher activity than the individual metals. Electronic properties of metals with largely filled valence bands (such as noble metals) can be altered by mixing the metal with another metal that possesses an almost empty valence band. Similar effects are observed by combining metals with similar valence characteristics, as is the case with noble metal deposition on noble metal substrates (e.g. Pd/Pt, Ru/Pt, Os/Pt). Well-defined single crystal substrates allow fundamental investigations of organic reactions on such bimetallic catalytic surfaces and provide valuable mechanistic insights.; In recent years, fuel cell technology has become an intense focus of the energy research community as a potentially viable alternative to emissions-producing devices. Both methanol and formic acid are promising fuels for this type of technology; however, to maintain catalytic efficiency and purity, the platinum anode must be modified by another metal, altering the electronic and catalytic properties of the platinum favorable toward methanol or formic acid oxidation. Palladium is known to enhance the catalytic activity of platinum towards formic acid oxidation while ruthenium and osmium increase the effectiveness of the catalyst toward methanol electrooxidation. Scanning Tunneling Microscopy (STM), X-Ray Photoelectron Spectroscopy (XPS) and electrochemical methods are ideal techniques to probe the structure and catalytic activity of platinum surfaces modified by noble metal adatoms. STM and XPS studies correlate surface coverage and composition with electrochemical activity and provide a valuable method for determining highly active modified platinum substrates for methanol oxidation. |
