Enhancing activity and stability of Co-MOF-74 for oxygen evolution reaction by wrapping polydopamine

Metal organic frameworks (MOFs) have attracted much attention as high-performance oxygen evolution reaction (OER) catalysts, while many strategies were used to enhance the OER performance of MOFs. However, few strategies were concerned on the effect of the MOF oxidation on the OER activity. Herein, using Co-MOF-74 as a model material, we elucidated that it is the cobalt on the oxidized MOF playing the role of active sites rather than pristine Co sites in Co-MOF-74. Strong evidence was shown that the redox process on Co sites in Co-MOF-74 occurred completely at potentials lower than that of OER taking place, accompanying with the collapse of Co-MOF-74 structure. Based on this, polydopamine (PDA) was used to modify Co-MOF-74 to promote the oxidation of Co sites to enhance the OER performance. Furthermore, the structure of Co-MOF-74 was well maintained by enwrapping PDA. As a result, the PDA enwrapped catalyst (PDA-MOF-0.1) exhibited a higher OER activity and an improved stability compared to pure Co-MOF-74.