The utilization of nano zero-valent iron (nZVI) in polybrominated diphenyl ethers remediation has been studied extensively. However, challenges in balancing cost and reactivity have been encountered. A submicron zero-valent iron coated with FeC2O4·2 H2O layers (OX-smZVI) was synthesized via a mechanochemical method, aiming to resolve this contradiction. Characterization via SEM, TEM, and XPS confirmed the structure as FeC2O4·2 H2O coated iron lamellate with a surface area 24-fold higher than ball-milled zero-valent iron (smZVI). XRD highlighted an Fe/C eutectic in OX-smZVI, boosting its electron transfer capacity. Decabromodiphenyl ether degradation by OX-smZVI follows a two-stage process, with initial degradation by FeC2O4·2 H2O and a subsequent phase dominated by electron transfer. OX-smZVI exhibits a 4.52–34.40 times faster BDE209 removal rate than nZVI and scaled-up OX-smZVI displayed superior reactivity with preparation costs only 1/680 of nZVI. Given its enhanced reactivity and cost-efficiency, OX-smZVI emerges as a promising replacement for nZVI. Display omitted •The degradation rate of OX-smZVI for BDE-209 was more than 4.52 times higher than that of nZVI.•The preparation cost of OX-smZVI was 1/680 of nZVI.•Scaled-up preparation (tens of kilograms at a time) of OX-smZVI exhibited even higher reactivity than laboratory OX-smZVI.•Fe(II) and direct electron transfer was responsible for BDE-209 debromination.•This work offers an available, inexpensive and efficient reductant for practical PBDEs remediation.