Incorporation of Transition Metal Substituents Into LaNiO ₃ Improves Electrocatalytic Activity and Stability of Acidic Oxygen Evolution

In this work, the crucial role of acid‐stable transition metals, namely, Mo, W, and Mn incorporated into LaNiO 3 (LNO) catalysts for the electrocatalytic oxygen evolution reaction (OER) in acidic conditions is elucidated. By means of high‐throughput experimentation, materials libraries of LNO with substituent concentration gradients ranging from 20 to 55 at‐% are synthesized. Based on a wide range of high‐throughput electrochemical screening techniques, including cyclic voltammetry, linear sweep voltammetry, and chronoamperometry, the OER activity in 0.1 M Na 2 SO 4 aqueous solution (pH = 4.1), is investigated. The results demonstrate high activity and superior stability compared to pristine LNO and Ir‐based benchmark electrocatalysts. The identified hit compositions, LNO‐Mo (35 at‐%) and LNO‐W (20 at‐%), exhibit an overpotential of 650 and 688 mV, respectively, more than 100 mV lower than pristine LNO, while simultaneously increasing the stability up to 240%. Finally, a set of physical characterizations (scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction), provides mechanistic insight into the relation between composition, electronic properties, and structure of the different substituted LNO and the improved acidic OER activity and stability. The hit candidates can be used in the future in proton exchange membrane electrolyzers to generate green hydrogen, assisting with climate change mitigation.