Efficient reduction of hexavalent chromium with microscale Fe/Cu bimetals: Efficiency and the role of Cu

Microscale zero valent iron (mFe0) is one of the most potential water pollution remediation materials, but the effective utilization ability of electrons released by mFe0 in the reduction of hexavalent chromium (Cr(VI)) is not satisfactory. Here, we find the microscale iron-copper (mFe/Cu) bimetals coated with copper on the surface of mFe0 can significantly improve the effective utilization of electrons released by mFe0. Electrochemical analysis displays that copper plating on the surface of mFe/Cu can promote the release the electrons from mFe0 and reduce the impedance of mFe0. Spin-polarized density functional theory (DFT) calculation reveals that Cu on the surface of mFe/Cu bimetals promotes the release of electrons from mFe0 and reduces the adsorption energy of Fe to Cr. As the electron transporter, moreover, Cu can always attract Cr to the hollow position near itself of the Fe surface, which could promote the effective utilization of electrons released by Fe. Effective utilization ability of electrons in mFe/Cu system is 12.5 times higher than that in mFe0 system. Our findings provide another basis for the efficient reduction of Cr(VI) by mFe/Cu bimetals, which could promote the application and popularization of mFe/Cu bimetals.