The role of electrolyte pH on water oxidation for iridium oxides was investigated using operando optical spectroscopy, X-ray absorption spectroscopy (XAS), and surface-enhanced infrared absorption spectroscopy (SEIRAS). The study reveals that the active species for the oxygen evolution reaction (OER), $Ir^{4+x}-*O$, binds more strongly in alkaline compared to acidic electrolytes at low coverage, but repulsive interactions between these species are higher in alkaline electrolytes. These differences are attributed to the larger fraction of water within the cation hydration shell at the interface in alkaline electrolytes, which can stabilize oxygenated intermediates and facilitate long-range interactions between them. Quantitative analysis of the state energetics shows that although the $*O$ intermediates bind more strongly than optimal in alkaline electrolytes, the larger repulsive interaction between them results in a significant weakening of $*O$ binding with increasing coverage, leading to similar energetics of active states in acid and alkaline at OER-relevant potentials. The study also shows that the interfacial water structure in alkaline electrolytes is different from that in acidic electrolytes, with a higher concentration of polar water molecules, which can stabilize oxygenated intermediates and facilitate long-range interactions between them. The results suggest that the interaction parameter between the $*O$ species is significantly different in acidic and alkaline electrolytes, with a higher value in alkaline electrolytes. These findings highlight the crucial role of electrolyte pH in controlling the OER kinetics of iridium oxides and provide insights into how the solvent effects can be exploited to increase catalytic activity. The study also demonstrates that the interaction energy between adsorbates can be directly probed using operando spectroscopy, which can explain the differences in redox transitions and OER activity in acid and alkaline electrolytes. The results suggest that the interfacial electrolyte structure plays a critical role in facilitating these interactions and that optimizing the catalyst–electrolyte interactions could potentially unlock the activity of previously thought to be inactive catalysts.The role of electrolyte pH on water oxidation for iridium oxides was investigated using operando optical spectroscopy, X-ray absorption spectroscopy (XAS), and surface-enhanced infrared absorption spectroscopy (SEIRAS). The study reveals that the active species for the oxygen evolution reaction (OER), $Ir^{4+x}-*O$, binds more strongly in alkaline compared to acidic electrolytes at low coverage, but repulsive interactions between these species are higher in alkaline electrolytes. These differences are attributed to the larger fraction of water within the cation hydration shell at the interface in alkaline electrolytes, which can stabilize oxygenated intermediates and facilitate long-range interactions between them. Quantitative analysis of the state energetics shows that although the $*O$ intermediates bind more strongly than optimal in alkaline electrolytes, the larger repulsive interaction between them results in a significant weakening of $*O$ binding with increasing coverage, leading to similar energetics of active states in acid and alkaline at OER-relevant potentials. The study also shows that the interfacial water structure in alkaline electrolytes is different from that in acidic electrolytes, with a higher concentration of polar water molecules, which can stabilize oxygenated intermediates and facilitate long-range interactions between them. The results suggest that the interaction parameter between the $*O$ species is significantly different in acidic and alkaline electrolytes, with a higher value in alkaline electrolytes. These findings highlight the crucial role of electrolyte pH in controlling the OER kinetics of iridium oxides and provide insights into how the solvent effects can be exploited to increase catalytic activity. The study also demonstrates that the interaction energy between adsorbates can be directly probed using operando spectroscopy, which can explain the differences in redox transitions and OER activity in acid and alkaline electrolytes. The results suggest that the interfacial electrolyte structure plays a critical role in facilitating these interactions and that optimizing the catalyst–electrolyte interactions could potentially unlock the activity of previously thought to be inactive catalysts.