As　an　environmentally-benign　and　sustainable　option　for　NH3　synthesis,　the　electrochemical　nitrogen　reduction　reaction　(NRR)　is　expected　to　replace　the　traditional　Haber-Bosch　process.　Transition　metals　with　empty　d-orbitals　achieve　NRR　activity　via　a　＂pi　back-donation＂　process.　However,　the　problem　in　overcoming　hydrogen　evolution　reaction　(HER)　competition　makes　the　exploration　of　transition　metal-based　catalysts　with　relatively　inferior　HER　activity　worthwhile.　The　challenges　lie　in　designing　a　rational　structure　for　efficient　NRR.　Herein,　Ni3+　and　oxygen　vacancies　were　synergistically　integrated　on　NiO@TiO2　by　magnetron　sputtering,　which　provide　this　transition-metal　oxide-based　(TMO-based)　material　with　＂pi　back-donation＂　behavior.　Accordingly,　NiO@TiO2　exhibited　NH3　yield　(similar　to　10.75　mu　g　h(-1)　cm(cat.)(-2))　and　faradaic　efficiency　(similar　to　9.83%),　which　are　nearly　10-fold　higher　relative　to　those　of　TiO2　in　neutral　media.　This　work　provides　an　efficient　strategy　for　engineering　＂pi　back-donation＂　sites,　and　holds　great　potential　in　exploring　new　TMO-based　electrocatalysts.