Water splitting systems rely heavily on the efficiency of the electrocatalytic oxygen evolution reaction (OER), which is a complex and multi-step process involving the conversion of diamagnetic hydroxyl species to paramagnetic oxygen molecules. This spin conversion requires additional energy and often leads to high overpotentials for most OER catalysts. Single atom catalysts (SACs) have emerged as a promising catalyst class due to their high specific single-atom metal sites, versatile coordination design, and efficiency. However, SACs can be prone to deactivation under harsh conditions, reducing their catalytic activity. In this study, we designed a NiCl₂dppp transition metal complex-based single molecule catalyst (SMC) immobilized on graphene acid (GA). In the NiCl₂dpp on GA (NiGA) catalysts, the SMC is stabilized by strong non-covalent interactions, such as H-bonding and pi-pi stacking. The resulting strong interfacial connection and preferential band alignment facilitate efficient electron transfer from NiCl₂dpp to GA, generating highly active interfacial catalytic sites for OER. Further, we identified in-situ structural changes of NiCl₂dppp under highly alkaline conditions, which transformed NiGA into a magnetic spin-active system, that can facilitate spin-polarized OER under an external magnetic field. When exposed to an applied magnetic field (~0.3T), the catalyst demonstrated a dramatic change in overpotential, reducing it from 290mV to 270mV at 1mA cm^-2 , and increasing the current density by 50%. Our control experiments confirmed spin-dependent OER activity with a low Tafel slope of 52mV Dec^-1 for NiGA. The findings suggest that in-situ and ex-situ structural tailoring of SMCs could provide a pathway for magnetically triggered spin-selected OER and water splitting systems.

Anju Yadav

Mechanistic characterization of phospholipid-functionalized single walled carbon nanotube abiotic sensors of molecules that disrupt cell membranes, university of texas at el paso

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