HNbxTa1-xWO6　monolayer　nanosheets　solid　solutions　were　successfully　synthesized　through　a　top-down　method.　The　crystal　structure　and　morphology　of　the　prepared　materials　were　investigated　by　X-ray　diffraction　patterns　(XRD),　Raman　spectra,　and　transmission　electron　microscopy　(TEM).　Atomic　force　microscopy　(AFM)　further　confirmed　that　the　thicknesses　of　the　nanosheets　solid　solutions　were　at　a　range　of　1.50–2.00 nm.　As　the　ratios　of　Nb　increased　from　x = 0.0　to　1.0　in　HNbxTa1-xWO6　nanosheets　solid　solutions,　the　photo-absorption　spectra　were　red-shifted,　showing　a　decrease　in　the　band　gaps　(from　3.26　to　3.10 eV),　and　the　flat　band　potentials　were　shifted　positively　(from　−0.78　to　−0.68 eV).　The　photocatalytic　activities　of　hydrogen　evolution　from　water　for　these　samples　were　found　to　be　strongly　dependent　on　their　composition,　which　would　increase　as　the　mole　ratios　of　Nb　to　Ta　increases.　Among　the　prepared　nanosheets　solid　solutions,　HNb0.7Ta0.3WO6　nanosheets　showed　the　highest　photocatalytic　activity　for　H2　evolution　with　a　rate　constant　of　1320.0 μmol h−1 g−1.　Combining　with　the　photo-electrochemical　analyses,　precise　control　of　the　energy　band　structure　via　a　solid　solution　strategy　is　a　useful　method　for　band　engineering　to　develop　an　efficient　photocatalyst.　©　2016　Elsevier　B.V.