A　new　class　of　hybrids　with　the　unique　electrocatalytic　nanoarchitecture　of　Fe1-xS　anchored　on　Fe3C-encapsulated　and　N-doped　carbon　nanotubes　(Fe1-xS/Fe3C-NCNTs)　is　innovatively　synthesized　through　a　facile　one-step　carbonization-sulfurization　strategy.　The　efficient　synthetic　protocols　on　phase　structure　evolution　and　dynamic　decomposition　behavior　enable　the　production　of　the　Fe1-xS/Fe3C-NCNT　hybrid　with　advanced　structural　and　electronic　properties,　in　which　the　Fe　vacancy-contained　Fe1-xS　showed　the　3d　metallic　state　electrons　and　an　electroactive　Fe　in　+2/+3　valence,　and　the　electronic　structure　of　the　CNT　was　effectively　modulated　by　the　incorporated　Fe3C　and　N,　with　the　work　function　decreased　from　4.85　to　4.63　eV.　The　meticulous　structural,　electronic,　and　compositional　control　unveils　the　unusual　synergetic　catalytic　properties　for　the　Fe1-xS/Fe3C-NCNT　hybrid　when　developed　as　counter　electrodes　(CEs)　for　dye-sensitized　solar　cells　(DSSCs),　in　which　the　Fe3C-　and　N-incorporated　CNTs　with　reduced　work　function　and　increased　charge　density　provide　a　highway　for　electron　transport　and　facilitate　the　electron　migration　from　Fe3C-NCNTs　to　ultrahigh　active　Fe1-xS　with　the　electron-donating　effect,　and　the　Fe　vacancy-enriched　Fe1-xS　nanoparticles　exhibit　ultrahigh　I3-　adsorption　and　charge-transfer　ability.　As　a　consequence,　the　DSSC　based　on　the　Fe1-xS/Fe3C-NCNT　CE　delivers　a　high　power　conversion　efficiency　of　8.67%　and　good　long-term　stability　with　a　remnant　efficiency　of　8.00%　after　168　h　of　illumination,　superior　to　those　of　traditional　Pt.　Furthermore,　the　possible　catalytic　mechanism　toward　I3-　reduction　is　creatively　proposed　based　on　the　structure-activity　correlation.　In　this　work,　the　structure　engineering,　electronic　modulation,　and　composition　control　opens　up　new　possibilities　in　constructing　the　novel　electrocatalytic　nanoarchitecture　for　highly　efficient　CEs　in　DSSCs.　©　Copyright　copy;　2018　American　Chemical　Society.