A　new　class　of　hybrids　with　the　unique　electrocatalytic　nanoarchitecture　of　Fe　1-x　S　anchored　on　Fe　3　C-encapsulated　and　N-doped　carbon　nanotubes　(Fe　1-x　S/Fe　3　C-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　Fe　1-x　S/Fe　3　C-NCNT　hybrid　with　advanced　structural　and　electronic　properties,　in　which　the　Fe　vacancy-contained　Fe　1-x　S　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　Fe　3　C　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　Fe　1-x　S/Fe　3　C-NCNT　hybrid　when　developed　as　counter　electrodes　(CEs)　for　dye-sensitized　solar　cells　(DSSCs),　in　which　the　Fe　3　C-　and　N-incorporated　CNTs　with　reduced　work　function　and　increased　charge　density　provide　a　highway　for　electron　transport　and　facilitate　the　electron　migration　from　Fe　3　C-NCNTs　to　ultrahigh　active　Fe　1-x　S　with　the　electron-donating　effect,　and　the　Fe　vacancy-enriched　Fe　1-x　S　nanoparticles　exhibit　ultrahigh　I　3　-　adsorption　and　charge-transfer　ability.　As　a　consequence,　the　DSSC　based　on　the　Fe　1-x　S/Fe　3　C-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　I　3　-　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.