A conceptual metallic/semiconducting TaB2/Ta2O 5 core/shell heterostructure exhibits a substantial improvement in photocatalytic hydrogen evolution rate under both UV and visible light. TaB 2 plays a dual role in boosting the photocatalytic activity by extending the light-absorption range via efficient interfacial electronic modification and by promoting the separation and transfer of photoexcited charge carriers by using metallic TaB2 core as an electron collector.