In situ identification of the electrocatalytic water oxidation behavior of a nickel-based metal-organic framework nanoarray

Metal-organic frameworks (MOFs) have been identified as one of the promising electrocatalysts for the oxygen evolution reaction (OER). However, direct observation of the electrocatalytic behavior of MOF-based electrocatalysts remains extremely challenging, which is of great significance to understand their electrocatalytic mechanism. Herein, we developed a vertically oriented Ni-based MOF nanosheet array doped with 2.09 wt% Ce (denoted as Ce-NiBDC/OG). Ce-NiBDC/OG displayed a low overpotential of 265 mV to deliver a 10 mA cm(-2) current density for the OER. In situ spectroscopy and operando microscopy visualized the phase transformation behavior of Ce-NiBDC/OG to Ce-doped NiOOH induced by electrochemical activation, which was regarded as the real active site. Mechanistic studies revealed that, for the Ce-NiBDC/OG-derived catalyst, the doping of Ce species in NiOOH significantly increased the adsorption of *OH, and further reduced the energy barriers of the rate-determining step (*OH ->*O).

Automated summary

The Ce-NiBDC/OG exhibited a low overpotential for the OER, with in situ spectroscopy and operando microscopy revealing the phase transformation behavior to Ce-doped NiOOH as the active site. Ce species doping in NiOOH was found to significantly enhance *OH adsorption and reduce the energy barriers for the rate-determining step (*OH -> *O) in the Ce-NiBDC/OG-derived catalyst.