van　der　Waals　(vdW)　heterostructures,　achieved　by　binding　various　two-dimensional　(2D)　materials　together　via　vdW　interaction,　expand　the　family　of　2D　materials　and　show　fascinating　possibilities.　In　this　work,　we　have　systematically　investigated　the　geometrical　structures,　electronic　structures,　and　optical　properties　of　III-VI　(MX,　M　=　Ga,　In　and　X　=　S,　Se,　Te)　vdW　heterostructures　and　their　corresponding　applications　in　sustainable　energy　related　areas　based　on　first　principles　calculations.　It　is　highlighted　that　different　heterostructure　types　can　be　achieved　in　spite　of　the　similar　electronic　structures　of　MX　monolayers.　Meanwhile,　the　potential　applications　of　the　heterostructures　for　sustainable　energy　related　areas　have　been　further　unraveled.　For　instance,　type-II　InS/GaSe　and　GaS/GaSe　vdW　heterostructures　can　separately　produce　hydrogen　and　oxygen　at　the　opposite　parts.　On　the　other　hand,　a　type-II　GaSe/GaTe　heterostructure　with　a　direct　band　gap　compatible　with　silicon　has　been　proposed　to　be　a　potential　solar　cell　material　with　a　power　conversion　efficiency　over　18%.　Furthermore,　a　gapless　type-IV　semi-metallic　InTe/GaS　heterostructure　has　been　predicted　to　be　a　Li-ion　battery　anode　material　based　on　three-step　lithiated　analysis.　The　present　results　will　shed　light　on　the　sustainable　energy　applications　of　such　remarkable　artificial　MX　vdW　heterostructures　in　the　future.　©　The　Royal　Society　of　Chemistry.