Unitized　regenerative　fuel　cells　operate　in　not　only　fuel　cell　but　also　water　electrolyzer　mode.　Heat　management　is　important　for　the　stable　operation　of　unitized　regenerative　fuel　cells.　In　this　work,　temperature　and　heat　flux　on　the　surface　of　the　gas　diffusion　layer　at　the　hydrogen　side　of　a　unitized　regenerative　fuel　cell　are　experimentally　measured　using　thin　film　sensors.　Four　pairs　of　sensors　with　good　linear　relation　coefficient　are　inserted　in　the　unitized　regenerative　fuel　cell.　The　variation　of　temperature　and　heat　flux　on　the　gas　diffusion　layer　surface　during　mode　switching　is　obtained.　The　effect　of　mode　switching　on　temperature　and　heat　flux　in　the　unitized　regenerative　fuel　cell　is　analyzed.　Experimental　results　show　that　reactant　switching　significantly　affects　temperature　and　heat　flux.　Reactant　switching　also　causes　decreased　temperature　and　variation　in　heat　flux.　Despite　of　the　decrease　of　temperature　caused　by　the　low-temperature　water,　the　temperature　increases　with　the　operation　of　the　URFC.　When　the　effect　of　reactant　switching　is　ignored,　temperature　is　further　found　to　increase　in　fuel　cell　and　water　electrolyzer　modes,　and　heat　flux　remains　relatively　stable.　(C)　2018　Hydrogen　Energy　Publications　LLC.　Published　by　Elsevier　Ltd.　All　rights　reserved.