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• The (Fe x , Co y)-NG/mpg-C 3 N 4 materials exhibited excellent activity due to the synergistic effect of well-defined dual sites. The photocatalytic hydrogen evolution reaction is a promising and powerful approach to replace traditional fossil fuels. Herein, we have fabricated Fe, Co dual single atoms dispersed on nitrogen-doped graphene ((Fe x , Co y)-NG) by freeze-drying method, which can as a highly efficient co-catalyst. The (Fe x , Co y)-NG loaded mesoporous graphitic carbon nitride (mpg-C 3 N 4) exhibits an excellently high performance for photocatalytic hydrogen evolution. The high activity can belong to two ways: (i) the ultrathin mpg-C 3 N 4 not only increases the absorption and active sites but also shortens the charge migration distance; (ii) The nitrogen functional groups from NG can provide abundant coordination sites to evenly bind Fe and Co atoms. The photocatalytic hydrogen evolution performances (Fe x , Co y)-NG co-catalyst with different content ratios of Fe atoms and Co atoms were also investigated. The optimized hydrogen production rate (1958 μmol g−1) of 5 wt% (Fe 0.2 , Co 0.8)-NG/mpg-C 3 N 4 is obviously higher compared to the monometallic counterparts (5 wt% Fe-NG/mpg-C 3 N 4 or 5 wt% Co-NG/mpg-C 3 N 4). The higher photoactivities are due to the synergistic effect between Fe and Co. [ABSTRACT FROM AUTHOR]