The oxygen evolution reaction (OER) is the oxidative half of water electrolysis and the main cause of energy loss during the reaction. Herein, confined OER catalysts were engineered by intercalating transition metals into zirconium phosphate (ZrP) nanoparticles. Another system was engineered where the metals are only incorporated on the surface of ZrP. It was found that the surface-based catalysts are more active than their intercalated counterparts by using the overpotential at 10 mA/cm² as the activity metric. Following this result, it was hypothesized that exfoliating ZrP can serve as better supports for these transition metals as they may provide more active sites for the OER than bulk ZrP nanoparticles. Exfoliation of ZrP was accomplished with tetra-n-butyl ammonium hydroxide (TBA⁺OH^-) and the exfoliated nanosheets were modified with transition metals by performing an ion-exchange reaction. Nickel and cobalt-modified exfoliated ZrP showed an improved activity compared to that of surface-modified ZrP nanoparticles. More specifically, the nickel sample had an overpotential of 400 mV, 100 mV less than the surface-based system. Meanwhile, cobalt-modified exfoliated ZrP showed an overpotential of 453 mV, 73 mV less than the surface-modified system. Furthermore, ZrP was also nanostructured to produce different morphologies and were subsequently modified each with nickel and cobalt. Herein, a comprehensive electrochemical activity comparison is made between all metal-modified samples with different support morphology. Results indicate that the morphology of ZrP supports affects the loading and coverage of Co and Ni species, explaining their different OER performances. All metal-modified samples were tested for their OER activity in a three-electrode electrochemical cell using a Rotating Disk Electrode (RDE) configuration with 0.1 M KOH as the electrolyte. Finally, preliminary in-situ X-ray absorption spectroscopy show initial results on the nature of the metals during operando conditions.

Mario Ramos-Garces

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