The conversion of solar energy into hydrogen fuels by semiconductor photocatalysts has been paid great attention in recent years. g-C3N4 has emerged as a rising star in this area for its numerous advantages. In this work, trace-amount phosphorus and sodium co-doped g-C3N4 is prepared by polymerizing the mixed precursors of melamine and sodium tripolyphosphate. The resultant photocatalyst exhibits remarkably enhanced photocatalytic performance in H-2 production. Experimental analysis and theoretical calculation indicate that such performance enhancement is mainly due to the improved charge transfer and separation resulting from the interstitial doping of sodium and phosphorus, as well as the more porous structure with enlarged specific surface area. (C) 2017 Elsevier B.V. All rights reserved.