Pushing the Operation Current Density of Alkaline Water Oxidation above 1 A cm2 via Electrocatalyst Engineering

Abstract Rapid cost reduction of green hydrogen is essential for the large‐scale deployment of hydrogen‐based energy system. A major component in achieving this is the development of advanced water electrolyzers. Sluggish oxygen evolution reaction (OER) is the bottleneck for water electrolysis, and tremendous efforts have been devoted to develop electrocatalysts that accelerate the OER kinetics. Recent advances have highlighted the potential of precious metal‐free OER electrocatalyst capable of stable operation at current densities above 1 A cm 2 . This brings an opportunity of constructing new‐generation electrolyzer with lower cost and higher productivity. However, achieving such high operating current densities presents new challenges. This review summarize the recent progress of high‐performance OER catalysts, and identifies key factors that can be leveraged to enhance catalyst activity. These factors include interface/surface engineering, amorphous and crystal phase coupling, hierarchical structure design, structural reconstruction and phase conversion, high entropy catalyst, and defect engineering. Additionally, the pressing challenges that have been largely ignored in previous research is addressed, such as sustaining long‐term stability under crucial conditions, disadvantages of immobilized powder electrocatalysts, electrode scale design, the necessity of designing innovative electrolyzer cell designs and advance characterization techniques.