Coupling Experimental and Simulated Spectroscopy to Resolve Structural Motifs in Ni-based (oxy)hydroxide

Ni-based (oxy)hydroxides shows promising potential as electrocatalyst for oxygen evolution reaction. Their catalytic performance is closely associated with dynamic restructuring of surface and bulk phases under applied potential. However, the microscopic mechanisms linking local bonding and electronic structure to catalytic activity remain poorly understood. In this work, we integrate experimental and first- principles spectroscopic approaches to elucidate the redox evolution of nickel (oxy)hydroxides. Raman spectra simulated using density functional theory (DFT), together with X-ray absorption spectra modeled within the muffin-tin approximation, reveal distinct vibrational and electronic signatures associated with different local bonding environments. Comparison between simulated and experimental Raman spectra provides spectroscopic fingerprints that enable the identification of bulk redox phases. The computed Raman response further exhibits sensitivity to hydrogen configurations in partially deprotonated structures, highlighting the influence of local proton ordering on lattice dynamics and phase stability. Complementary XAS simulations probe site-specific electronic transitions and local coordination in both ordered and disordered nickel (oxy)hydroxide clusters. The spectral fine structure reflects variations in Ni–O bond covalency and oxidation state, enabling quantitative correlation between electronic structure and catalytic activity. This integrated approach provides a pathway to interpret the structural evolution of Ni-based electrocatalysts and to guide the design of more efficient oxygen-evolving materials.