A　first-principles　study　of　adsorption　and　diffusion　of　OH　on　Pt　and　PtMo　(111)　surfaces　is　described.　It　confirms　that　the　dissociation　of　water　is　much　easier　on　PtMo　than　on　pure　Pt.　Furthermore,　we　also　found　that　OH　binds　most　strongly　at　Mo　atop　site　with　adsorption　energy　of　-3.32　eV,　which　is　similar　to　1　eV　stronger　than　binding　to　the　pure　Pt(111)　surface.　OH　is　much　more　localized　on　the　PtMo　alloy　surface　than　on　pure　Pt.　Both　the　stranger　bond　and　the　higher　localization　of　OH　contribute　to　the　enhanced　fuel　cell　performance　with　PtMo　electrodes　compared　to　pure　Pt.　(c)　2007　Elsevier　Ltd.　All　rights　reserved.