(418b) XPS and in-Situ SERS Investigations of Metal Boride Nanoparticles for the Oxygen Evolution Reaction

Water electrolysis to generate H₂, a potential fuel source or CO₂ reductant, provides a large-scale solution to sustainably meet growing energy demand. In order for this approach to be viable, however, highly efficient conversion of water to H₂ and O₂ must occur. Even the most active oxygen evolution reaction (OER) electrocatalysts demonstrate large overpotentials due to the slow kinetics of this reaction. While iridum is the best elemental catalyst for the OER in alkaline electrolyte, the high abundance and stability of Ni and Ni-based alloys result in their predominant use within commercial electrolyzers. In particular, alloys of Ni with B or Fe have shown high activity for the OER, though little is known about the effects of B and Fe addition to Ni.

To investigate Ni-B and -Fe alloys for the OER, NiO_x, Ni_2.5B, Ni_1.3FeO_X and Ni_1.7FeB_1.2 nanoparticle electrocatalysts were prepared and studied. Activity comparisons were also made to FeO_x, Fe₂B, and bulk Ir. The OER activity increases in the order Fe₂B < NiO_X < Ni_1.3FeO_X < bulk IrO₂ < Ni_2.5B < Ni_1.7FeB_1.2, with the turnover frequency of Ni_1.7FeB_1.2 approximately double that of bulk Ir. In-situ surface-enhanced Raman spectroscopy (SERS) and ex-situ x-ray photoelectron spectroscopy (XPS) were used to determine the active phase and surface oxidation states of the Ni nanoparticle electrocatalysts, which are discussed in relation to observed OER activities.