Second-generation　biodiesel　is　the　dominant　biomass-derived　liquid　fuel　produced　from　nonedible　natural　or　waste　oils　and　fatty　acids　through　selective　oxygen　removal.　Here,　we　developed　a　highly　selective　sulfur-free　NiMo/TiO2　catalyst　by　disentangling　electronic　and　geometric　effects　to　produce　second-generation　biodiesel　via　the　hydrodeoxygenation　of　palmitic　acid-one　of　the　most　common　fatty　acids　in　these　feedstocks.　An　unprecedented　hexadecane　yield　of　96.0%　(on　a　mole　basis)　was　achieved　over　the　Ni1Mo1/TiO2　catalyst　(with　a　Ni:Mo　ratio　of　similar　to　1:1)　at　300　degrees　C　and　3　MPa　H2.　Kinetic　studies　reveal　that　the　competition　between　hydrodeoxygenation　(C-O　scission)　and　decarbonylation　(C-C　scission)　of　the　intermediate　hexadecanol　is　key　to　optimizing　selectivity.　Furthermore,　Mo　incorporation　markedly　lowers　the　apparent　activation　energy　of　hydrodeoxygenation-especially　in　the　Ni1Mo1/TiO2　catalyst,　which　has　the　lowest　Ni-Ni　coordination　number.　Combined　with　catalyst　characterization,　these　findings　elucidate　a　Mo-induced　＂Ni　coordination　environment＂-directed　reaction　pathway:　the　superb　hydrodeoxygenation　activity　and　selectivity　of　Ni1Mo1/TiO2　stem　from　its　abundant　NiMo　interfacial　sites,　where　Mo-induced　oxygen　vacancies　synergize　with　adjacent　Ni　sites　to　facilitate　the　adsorption　of　O-containing　groups　and　subsequent　C-O　bond　cleavage.