250415_cpy131_repro_ECbalanced_4

To study the effect of pre-conditioning on Co₃O₄ OER activity by tuning the catalyst during pre-OER by using different CV/LSV scan rates. This provides a comprehensive indication of the integrated charge (Q_imb), which can be used to classify the pre-conditioning protocols as charge balanced (Q_imb≈0), anodic excess (Q_imb>0), and cathodic excess (Q_imb<0) regimes.

To evaluate OER activity LSV and EIS will be applied. To reveal structural differences ex-situ Raman and XPS will be conducted as a post-electrochemical characterisation.

The freshly prepared ink of 1 µg/µL Co3O4 NPs (cpy131_repro) sonicated (Elmasonic P, 37 Hz, power = 100) in DI water for 15 min. A glassy carbon disk electrode with a geometric area of 0.5 cm2 (RDE) was polished (3.00 min, GCE polish disks 1 μm, 0.3 μm and 0.05 μm with Al2O3 suspension), loaded with 50 μL of ink by drop casting (micropipette, catalyst loading 100 µg cm-2), and dried for 30 min under Ar stream with heating at 65 oC. 200ml of 100mM KOH was Ar bubbled before experimant for 15 min.

• OCP
• EIS at OCP
• 10CVs (from OCP to 0.40V vs. Hg/HgO, scan rate 50 mV/s)
• 30CVs (from OCP to 0.60V vs. Hg/HgO, scan rate 50 mV/s)
• LSV (from OCP to 0.73 V vs. Hg/HgO, scan rate 5 mV/s)
• EIS @ 0.73V vs. Hg/HgO
• EIS @ 0.75V vs. Hg/HgO
• EIS @ 0.80V vs. Hg/HgO
• OCP