Two-dimensional　(2D)　MXenes　have　garnered　tremendous　interest　due　to　their　novel　properties.　In　the　present　study,　the　exfoliation　energy,　structural,　electronic　and　optical　properties　of　(Zr0.5Hf0.5)2CO2　have　been　investigated　by　density　functional　theory　calculations.　We　found　that　the　dynamically　and　thermally　stable　(Zr0.5Hf0.5)2CO2　have　ideal　band　gap,　high　redox　potential,　as　well　as　unexpectedly　high　carrier　mobility　and　efficient　separation　of　photogenerated　electron–hole　pairs.　It　is　highlighted　that　(Zr0.5Hf0.5)2CO2　shows　better　visible　light　harvest　than　pristine　Zr2CO2　and　Hf2CO2.　Additionally,　the　simulations　of　the　adsorption　and　decomposition　of　water　molecules　on　the　2D　(Zr0.5Hf0.5)2CO2　surface　have　been　studied　to　unravel　the　mechanism　of　the　hydrogen　production　process.　These　insights　provide　eloquent　evidence　that　(Zr0.5Hf0.5)2CO2　monolayer　is　potentially　an　efficient　visible-light　driven　water-splitting　photocatalyst.　©　2020　Elsevier　B.V.