Methanol　steam　reforming(MSR),　catalyzed　by　the　PdZn　alloy,　produces　hydrogen　gas　and　carbon　dioxide　with　high　selectivity.　However,　the　mechanism　for　MSR　has　not　been　completely　elucidated.　It　has　been　proposed　that　formate　and　methyl　formate　are　possible　intermediates　in　MSR.　In　this　study,　plane-wave　density　functional　theory　was　used　to　investigate　the　role　of　methyl　formate　in　MSR　on　PdZn.　It　is　shown　that　methyl　formate　can　indeed　be　formed　by　a　reaction　between　formaldehyde　and　methoxyl.　In　the　presence　of　surface　OH　species,　methyl　formate　can　further　react　to　form　formic　acid,　which　can　finally　dehydrogenate　to　produce　CO2.　However,　our　calculations　show　that　this　hydrolysis　process　might　have　difficulties　competing　with　desorption　of　methyl　formate,　which　is　weakly　adsorbed　on　the　PdZn　surface.　Our　calculated　results　thus　suggest　a　minor　role　for　the　methyl　formate　pathway　in　MSR.　Interestingly,　the　methyl　formate　reaction　pathway　shares　many　similarities　with　the　same　process　on　copper,　which　is　the　traditional　catalyst　for　MSR.　The　insights　gained　by　studying　the　reaction　mechanism　on　these　two　surfaces　shed　valuable　light　on　designing　future　catalysts　for　the　MSR　process.　(C)　2012　Elsevier　B.V.　All　rights　reserved.