The　development　of　phase　change　materials　(PCMs)　is　hampered　by　issues　like　leakage,　poor　thermal　conductivity,　and　poor　light　absorption.　In　this　study,　we　innovatively　combined　modified　melamine　foam　(MF)　and　graphene　nanoparticle　(GNP)　to　address　these　defects　of　PCMs　in　the　solar-thermal　energy　system.　The　MF　was　modified　to　endow　the　solar-thermal　energy　conversion　ability　and　superhydrophobic　interface　characteristics　due　to　the　polypyrrole　(PPy)　by　the　in-situ　polymerization　and　the　polymerized　octadecylsiloxane　(PODS)　layer　coating　on　the　sponge　skeleton.　The　composite　PCMs　consisting　of　the　modified　MF,　paraffin　wax　(PW),　and　GNP　were　fabricated　and　exhibited　good　leakproof　ability,　high　thermal　conductivity,　and　excellent　solar-thermal　energy　conversion　capability.　Results　showed　that　due　to　the　effects　of　the　PPy　and　the　PODS　on　the　sponge　skeleton　structure,　MF@PPy-PODS/PW　composite　PCMs　showed　a　decrease　in　the　mass　loss　ratio　to　less　than　0.34%　and　an　increase　in　the　thermal　conductivity　of　0.33　W/m·K　and　the　solar-thermal　storage　efficiency　of　75.68%.　Besides,　adding　GNP　with　higher　concentrations　impacted　positively　on　the　thermal　conductivity　and　the　solar-thermal　energy　conversion　ability　but　negatively　on　the　phase　change　enthalpies.　MF@PPy-PODS/GNP3/PW　composite　PCMs　increased　the　thermal　conductivity　to　0.59　W/m·K　and　the　solar-thermal　storage　efficiency　to　79.36%　while　decreasing　the　phase　change　enthalpy　to　130.61　J/g.　Furthermore,　a　thermoelectric　conversion　system　driven　by　solar　energy　was　developed　to　show　the　potential　of　composite　PCMs　for　cleaner　energy　production.　The　open-circuit　voltages　of　the　MF@PPy-PODS/GNP3/PW　composite　PCMs　achieved　0.78　and　0.91　V　at　2　and　4　Sun,　respectively.　The　open-circuit　voltages　remained　for　a　period　of　time　and　slowly　dropped　without　the　simulated　solar　light　irradiation.　This　study　provided　a　potential　strategy　for　the　optimal　performance　of　composite　PCMs　and　their　application　in　solar　thermal　systems.　©　2022　Elsevier　Ltd