Reconstruction and Dissolution of Transition Metal (Oxy)Hydroxide Electrocatalysts Induced By Intermittent Water Electrolysis
Authors: Marquez Raul A. , Kalokowski Emma , Le Thuy Vy , Williamson Chloe L. , Kawashima Kenta , Bender Jay T , Dolocan Andrei , Celio Hugo , Milliron Delia J , Resasco Joaquin , Jaramillo Thomas F. , Mullins C Buddie 
Published: December 2024

Electrochemical water splitting is essential in current decarbonization efforts, requiring catalysts that combine high activity with stability. First-row transition metal oxides have been extensively studied due to their remarkable chemical and physical attributes. Their significant catalytic activity and durability in alkaline environments make them a cost-effective alternative to noble metal counterparts in acidic conditions. However, recent research indicates that catalysts composed of transition metals like Ni, Co, Fe, and Mn undergo dissolution and substantial changes in their chemical composition during operation.1–3 Addressing these issues is vital for the progress of commercial energy conversion technologies, which frequently experience intermittent loads and reverse currents. Thus, gaining a comprehensive understanding of the reconstruction processes these materials undergo under fluctuating current conditions is key to developing more resilient and efficient electrocatalytic materials.4

Herein, we investigate the dissolution and compositional transformations of metal (oxy)hydroxide electrocatalytic films during steady and intermittent operation. These films, tested as oxygen evolution reaction catalysts in alkaline media, consisted of nickel oxyhydroxide codeposited with cobalt, iron, and manganese on titanium substrates. Inspired by recent findings on the effect of pH swings during high current electrolysis,5 we examined the electrode potential transients of these films under steady and intermittent current operation in a typical three-electrode configuration. We used time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy to analyze compositional changes in the electrocatalytic films before and after testing. Next, we conducted ex-situ and online inductively coupled plasma mass spectrometry measurements to track metal dissolution under different testing environments. To evaluate if these phenomena persist in more practical environments, we utilized an electrochemical flow electrolyzer developed by our group to examine the reconstruction of these electrocatalysts under intermittent, industry-relevant conditions. Our research highlights the influence of operational conditions on the reconstruction and dissolution of electrocatalytic materials, providing vital insights for developing more durable and efficient materials.

References:

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