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Chenglong Luan, Johanna Angona, Arjun Bala Krishnan, Manuel Corva, Seyed Pouya Hosseini Yazdeli, Markus Heidelmann, Ulrich Johannes Hagemann, Emmanuel Batsa Tettah, Wolfgang Schuhmann, Kristina Tschulik, Tong Li

• The role of \(\beta\)-CoOOH crystallographic orientations in catalytic activity for the oxygen evolution reaction (OER) remains elusive. We combine correlative electron backscatter diffraction/scanning electrochemical cell microscopy with X-ray photoelectron spectroscopy, transmission electron microscopy, and atom probe tomography to establish the structure–activity relationships of various faceted \(\beta\)-CoOOH formed on a Co microelectrode under OER conditions. We reveal that \(\approx\)6 nm \(\beta\)-CoOOH(01\(\overline{1}\)0, grown on [\(\overline{1}\)2\(\overline{1}\)0]-oriented Co, exhibits higher OER activity than \(\approx\)3 nm \(\beta\)-CoOOH(10\(\overline{1}\)3) or \(\approx\)6 nm \(\beta\)-CoOOH(0006) formed on [02\(\overline{2}\)1]- and [0001]-oriented Co, respectively. This arises from higher amounts of incorporated hydroxyl ions and more easily reducible Co\(^{III}\)−O sites present in \(\beta\)-CoOOH(01\(\overline{1}\)0) than those in the latter two oxyhydroxide facets. Our correlative multimodal approach shows great promise in linking local activity with atomic-scale details of structure, thickness and composition of active species, which opens opportunities to design pre-catalysts with preferred defects that promote the formation of the most active OER species.