Graphene is an advanced carbon energy material due to its excellent properties. Reduction of graphene oxide (GO) is the most promising mass production route of graphene/reduced graphene oxide (rGO). To maintain graphene’s properties and avoid restacking of rGO sheets in bulk, the preparation of 3-dimensional porous graphene sponge via 2-dimensional rGO sheets is considered as a good strategy. This article presents a facile route to synthesize graphene sponge by thermal treating GO powder at low temperature of 250 °C under N2 atmosphere. The sponge possesses macroporous structure (5–200 nm in size) with BET specific surface area of 404 m2 g–1 and high conductivity. The photocatalytic H2 production activity of the rGO sponge with a sensitizer Eosin Y (EY) and cocatalyst Pt was investigated. The rGO sponge shows highly efficient dye-sensitized photocatalytic H2 evolution compared to that obtained via a chemical reduction method. The maximum apparent quantum yield (AQY) reaches up to 75.0% at 420 nm. The possible mechanisms are discussed. The synthesis method can be expanded to prepare other graphene-based materials.