All chemicals were obtained from Signa Aldrich and used without further purification. FeSO4, ascorbic acid and sodium citrate were combined with deoxygenated DI H2O as solution A (0.3M, 0.675M, 0.5M respectively). Na-HCF was combined with deoxygenised H2O (deoxygenated by bubbling N2 gas through deionized (DI) H2O) to form solution B. The solutions were slowly mixed under stirring at 65 o C with a mixing rate of 3 ml h -1 . The samples were aged in solution for 24 h followed by a semi-inert filtering with 300 ml deoxygenated DI H2O. The samples were dried at RT under N2 flow and stored in an argon glove box until use.