Understanding　the　variation　in　heat　and　mass　transfer　during　mode　switching　of　a　unitized　regenerative　fuel　cell　is　essential　for　designing　efficient　flow　channels　and　operational　strategies.　In　this　study,　dynamic　variation　of　current　density,　temperature,　and　species　distribution　during　mode　switching　is　investigated　in　a　unitized　regenerative　fuel　cell　with　a　stepped　flow　channel.　This　work　is　conducted　by　a　transient　multi-physics　model　coupled　with　electrochemical　reaction,　heat　and　mass　transfer,　and　phase　change.　Results　indicate　that　the　response　time　of　current　and　temperature　is　prolonged　as　the　mode-switching　frequency　rises.　Using　stepped　channels　instead　of　conventional　straight　channels　can　promote　mode-switching　and　shorten　the　response　time.　Specifically,　the　stepped　structure　promotes　airflow　disturbance　in　flow　channels,　and　the　induced　forced　convection　promotes　heat　and　mass　transfer.　Besides,　the　stepped　structure　accelerates　the　stabilization　of　current　density,　temperature,　and　species　during　mode　switching,　leading　to　a　more　uniform　current　density　distribution.　In　addition,　the　stepped　structure　promotes　water　discharge　and　convective　heat　transfer,　improving　the　temperature　uniformity　of　the　catalyst　layer.　This　study　offers　valuable　insights　for　improving　the　durability　of　the　membrane　electrodes　and　improving　the　operational　stability　of　unitized　regenerative　fuel　cells　during　mode　switching.　©　2024　Elsevier　Ltd