Exploring the Impact of the Spin-State of Transition Metal Dopants on OER in NiOOH Catalysts

Spin effects can play a key role in activity of electrocatalysts. For example, Fe-doping has long been known to strongly enhance the activity of NiOOH for the oxygen evolution reaction (OER) under alkaline conditions [1]. We have recently explained the origin of this enhancement through the low-spin state of the Fe dopant, with the predicted decrease in the thermodynamic overpotential for OER being consistent with measured values [2]. The considered scenario also explains other phenomena observed in this material, such as short Fe-O bond-lengths, and the ~25% solubility limit of Fe in NiOOH.<br/><br/>Following successful modelling of Fe-doped NiOOH, here we present a follow-up investigation by considering other transition metal dopants such as Co and Mn. In the periodic table these metal elements are positioned close to Fe and have thus received considerable attention as dopants to enhance the activity of NiOOH for OER [3,4]. We compare the computed results with available experimental data. We will emphasise the need for future studies to explore the previously-overlooked impact of the spin-state of transition metal cations on the catalytic performance mixed-element catalysts. Finally, we show the necessity of applying accurate computational methodologies for realistic, simulations-based characterization of energy materials.<br/><br/>[1] Friebel et al., J. Am. Chem. Soc. 137, 1305-1313 (2015)<br/>[2] He et al., Nat, Commun. 14, 3498 (2023)<br/>[3] Costanzo, Phys. Chem. Chem. Phys., 18, 7490 (2016)<br/>[4] Tkalych et al., Phys. Chem. Chem. Phys., 20, 19525 (2018)