Development of Catalysts for Oxygen Evolution Reaction in Alkaline Media

The looming threat of climate change and its consequences make it imperative for humankind to find alternatives to conventional energy sources. Green hydrogen, produced by splitting water into hydrogen and oxygen using renewable energy, is one way to address this problem. However, the high cost and low energy efficiency of conventional water electrolysis methods continue to restrict the widespread adoption of green hydrogen. In this work, we develop novel catalysts, investigate their structural and electrocatalytic properties and correlate their activity with the in situ evolution of active phases through operando Raman spectroscopy. We focus on a class of nickel-based materials, including NiFe nanoparticles on metal oxide supports, metal organic frameworks and metal organic complexes. In the first part, we investigate the catalytic activity of NiFe nanoparticles dispersed on metal oxide supports for the oxygen evolution reaction, employing electrochemical testing with an anion exchange ionomer to evaluate their potential for application in anion exchange membrane electrolyzers. We report the electrochemical performance of NiFe nanoparticles with varying Ni:Fe ratios on CeO2 for the oxygen evolution reaction, assessing the overpotential, Tafel slope and electrochemical stability of the catalysts. Our findings indicate that Ni90Fe10 exhibits the highest catalytic activity as well as excellent stability. To further elucidate the role of the support, we evaluate the electrocatalytic performance of Ni90Fe10 nanoparticles on two additional supports, TiO2 and ZrO2. While CeO2 provides the lowest overpotential, the other supports also show high activity and good performance at high current densities. TiO2 exhibits superior stability, and its overpotential after chronopotentiometry measurements approaches that of CeO2 at high current densities. These results underscore the critical role of iron addition in enhancing the catalytic activity of nickel nanoparticles and emphasize the importance of metal oxide supports in improving catalyst stability and performance. In the second part, we conduct an operando investigation into the electrochemical transformation of metal organic framework precursors into active Ni and NiFe oxyhydroxide catalysts for the oxygen evolution reaction. Using in-situ Raman spectroscopy alongside comprehensive electrochemical measurements, we demonstrate that the transformation pathway is strongly influenced by the linker chemistry and Fe doping. Notably, Ni catalysts synthesized with a terephthalic acid linker exhibit an earlier onset of NiOOH formation, as evidenced by the emergence of characteristic Ni–O vibrational modes near 475 and 560~cm-1. Detailed deconvolution of the broad OH stretching region (3200--3700~cm-1) further distinguishes the dynamics of intercalated and interfacial water. The intercalated water undergoes a blue shift, reflecting reduced hydrogen bonding upon deprotonation, while interfacial water exhibits a red shift under enhanced hydrogen bonding conditions at the electrode–electrolyte interface. These insights elucidate the critical role of water in mediating proton transfer and stabilizing the active phase, thereby providing molecular-level guidelines for the rational design of next-generation oxygen evolution reaction catalysts. In the third part, we report a novel nickel–2-methylimidazole complex with detailed structural characterization. Although the material exhibits a relatively short operational lifetime, it shows promising electrocatalytic activity for the oxygen evolution reaction under alkaline conditions. Our results reveal that this catalyst is more active when used with Aemion+ than with Nafion. We also examine the influence of dopants (Fe, Mn and Cu) on the activity of the material. In particular, the Fe-doped and trimetallic NiFeMn variants show superior OER performance compared with the undoped Ni complex. Operando Raman spectroscopy is used to monitor active phase evolution and to probe how NiOOH formation varies with different heteroatom dopants. Mn and Cu exhibit suppressor behavior, whereas Fe promotes OER activity. In the final phase, we use Bayesian optimization to refine the ink formulation for a MOF-based catalyst. Our results show that solvent composition, ionomer content and catalyst loading act together in a complex way to control the activity, providing practical guidelines for ink design.