Solar-driven　one-step　disproportionation　overall　nitrogen　fixation　(ONF)　for　synchronously　synthesizing　ammonia　and　nitrate　presents　a　promising　alternative　to　conventional　Haber-Bosch　and　Ostwald　processes,　but　suffers　from　ultra-low　efficiency.　Single　atoms　(SAs)　featured　by　maximized　atomic　utilization　exhibit　superb　catalytic　activity,　while　the　definite　electronic　configurations　confine　SAs　to　function　solely　as　reduction　or　oxidation　sites,　limiting　the　possibility　for　both　reduction　and　oxidation　reactions.　Herein,　an　efficient　approach　is　presented　for　ammonia　and　nitrate　co-synthesis　by　introducing　Fe　SAs　and　alternating　piezoelectric　field　into　a　defective　piezoelectric　BaTiO3　(OvBTO-Fe),　enabling　the　formation　spatially-separated　redox　regions　and　dynamic　bidirectional　switching　of　Fe　spin　states.　At　positive　and　negative　polarization　ends,　Fe　spin　state　transitions　to　high　and　low　spin　states　through　d-electrons　relocation,　respectively,　thermodynamically　and　kinetically　facilitate　nitrogen　reduction　and　oxidation　reactions.　Thus,　OvBTO-Fe　exhibits　unprecedented　piezo-photocatalytic　ONF　activity,　achieving　a　record　solar-to-chemical　conversion　efficiency　of　0.82%　and　total　energy-to-chemical conversion　efficiency　of　0.53%.　This　work　proposes　a　methodology　for　dynamic　multi-directional　manipulation　of　spin　states　and　overall　catalytic　synthesis　reaction.　©　2025　Wiley-VCH　GmbH.