Preparation: |
prepared following the procedure of Sugimoto et al. [39]. Briefly, 500 mL of a 2 M FeCl3 solution was slowly added over the course of 5 min to 500 mL of a propeller-stirred 5.4 M NaOH solution. The resulting gel was aged in tightly stoppered Pyrex® glass bottles at 101 °C for 8 days. After cooling to room temperature, the suspension was transferred into polypropylene centrifuge bottles. The product was repeatedly washed with doubly deionized (DDI) water (18.2 MΩ cm, MilliQ, Millipore) until
the electrical conductivity was below 5 µS cm-1 and then re-suspended in DDI water. |