(451f) Reconstruction of Transition Metal (Oxy)Hydroxide Electrocatalysts Induced By Intermittent Water Electrolysis

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 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 Ni, Co, Fe, and Mn undergo dissolution and substantial changes in their chemical composition during operation. 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.

Herein, we investigate the dissolution and compositional transformations of metal (oxy)hydroxide electrocatalytic films during intermittent operation. These films consist of Ni oxyhydroxide codeposited with Co, Fe, and Mn on Ti substrates. We examined the electrode potential transients of these films under steady and intermittent current operation in a three-electrode configuration. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) were employed to analyze compositional changes before and after testing. Next, we conducted ex-situ and online inductively coupled plasma mass spectrometry (ICP-MS) measurements to track metal dissolution. TOF-SIMS and XPS results confirm changes in the chemical composition of the films; Ni and Co are more stable than Fe and Mn. Ex-situ ICP-MS measurements also show higher concentrations of Mn and Fe after reverse current transients. To evaluate if these phenomena persist in more practical environments, we utilize an electrochemical flow electrolyzer to examine the reconstruction under industry-relevant conditions (in progress). Our research highlights the influence of operational conditions on the stability of electrocatalytic materials, providing vital insights for developing more efficient materials.