Enhanced　stability　and　prolonged　reactivity　of　nanoparticles　are　critical　factors　for　successful　applications　of　the　nanoscale　zero-valent　iron　(nZVI)　technology.　In　this　work,　g-C3N4　was　employed　as　a　support　for　distributing,　stabilizing　nZVI　and　further　changing　the　composition,　microstructure　and　electronic　structure　of　nZVI　due　to　the　interactions　between　the　iron　nanoparticles　and　g-C3N4　sheet.　Adjusting　the　micro-structure　of　nZVI　to　enhance　the　adsorption　ability,　control　the　electron　transfer,　shift　IEP　negatively,　and　improve　the　reactivities　and　stabilities　coordinatively　results　in　stabilized　and　long-term　effective　g-nZVI.　For　example,　the　accumulated　wastewater　(i.e.,　[Pb(II)]　=　10　mg/L)　treatment　volume　with　g-nZVI　in　5　runs　is　determined　to　be　50　L,　more　than　twice　the　treatment　capacity　of　bare　nZVI.　Besides,　more　Pb(II)　is　reduced　to　metallic　Pb　by　g-nZVI　than　that　by　nZVI.　Characterizations　with　spherical-aberration-corrected　scanning　transmission　electron　microscopy　(Cs-STEM)　integrated　with　X-ray　energy　dispersive　spectroscopy　(XEDS),　electron　energy　loss　spectroscopy　(EELS),　Raman　spectroscopy,　etc.　visualize　and　quantitatively　analyze　the　structural　differences　and　distinctive　reactive　behaviors　of　nZVI　and　g-nZVI.　The　N-containing　functional　groups　efficiently　capture　aqueous　metal　cations,　accelerate　mass　transfer　and　electron　transport　from　the　iron　core　to　surface-attached　metal　ions.　In　addition,　the　nZVI　micro-structure　change　and　the　formation　of　covalent　bonds　between　the　lone-pair　electron　of　nitrogen　and　empty　orbital　of　iron　apparently　reduced　the　iron　corrosion.　Results　provide　direct　evidence　on　the　interface　chemistry　of　g-nZVI　and　further　verify　the　graphitic　carbon　nitride　induces　the　Pb(II)　ions　to　be　deposited,　reduced　and　grown　onto　iron　nanoparticles.　©　2020　Elsevier　B.V.