New　types　of　photocatalytic　systems　formed　by　coupling　annealed　large-sized　NiFe-LDH　nanosheets　with　smallsized　TiO2　nanosheets　were　used　to　facilitate　the　rapid　separation　of　photo-generated　electrons　and　holes.　The　photocatalytic　hydrogen　production　for　optimized　photocatalytic　systems　can　reach　209　mmol/g,　which　is　8　times　of　that　for　TiO2.　To　understand　the　photocatalytic　mechanism,　in-situ　annealing　transmission　electron　microscopy　(TEM)　investigation　of　the　microstructural　evolution　of　large-sized　NiFe-LDH　nanosheets　identified　typical　microstructures　at　different　annealing　stages.　The　microstructure　of　the　optimized　system　contains　plentiful　ultrafine　grains　distributed　along　surface　delaminated　defects,　which　can　provide　abundant　active　sites　for　photocatalytic　hydrogen　evolution.　Electrochemical　and　spectroscopic　techniques　were　further　used　to　determine　the　Z-scheme　mechanism,　guiding　photo-generated　electrons　to　fast　transfer　onto　large-sized　NiFeLDH　nanosheets　to　achieve　high　efficient　carrier　separation.