Mixed Transition Metal Carbonate Hydroxide‐Based Nanostructured Electrocatalysts for Alkaline Oxygen Evolution: Status and Perspectives

Hydrogen is regarded as the cleanest and highest energy‐density fuel as an alternative energy resource. Water electrolysis is useful for producing ultrapure hydrogen (>99.9%), and alkaline water electrolysis is industrially adopted for large‐scale hydrogen production. However, the anodic oxygen evolution reaction (OER) remains as the bottleneck for achieving efficient hydrogen generation because of its multielectron pathways and sluggish kinetics. Additionally, the OER is crucial for other renewable energy conversion and storage systems, such as CO 2 reduction and metal–air batteries. In this regard, high‐performing, durable, and cost‐effective electrocatalysts are essential for achieving the desired hydrogen production efficiency. Recently, transition metal carbonate hydroxides (TMCHs) have been investigated as electrocatalysts for alkaline water splitting because of their layered structure, rich redox properties, and high accessibility to electrolytes. Furthermore, the electronic, morphological, and structural modulations in mixed TMCHs, due to the presence of multiple metal centers, offer more accessible active sites for the OER. Considering these aspects, the present review focuses on the application of mixed transition metal carbonate hydroxide (MTMCH)‐based nanostructured electrocatalysts to OER in alkaline media. This review will benefit the understanding and evaluation of OER activity and the development of MTMCH‐based electrocatalysts for practical application to the OER.