Green hydrogen production via water electrolysis is expected to become an environmentally friendly technology for decentralized and seasonal energy storage provided that the hydrogen production cost becomes competitive. An ideal catalyst for the oxygen evolution reaction (OER), the sluggish process in water electrolysis, should operate at low overpotential, exhibit long-term stability, and utilize low-cost materials. High-surface-area metal oxide/(oxy)hydroxide nanostructures have demonstrated promising characteristics as low-cost OER catalysts. These non-noble metal-based, high-surface-area catalysts, however, usually do not possess long-term stability in acidic or alkaline electrolytes, especially at high operating potentials which are required for practical applications. The causes of catalyst degradation may originate from either chemical/electrochemical processes or both. For example, cobalt oxide/(oxy)hydroxide nanostructures, extensively studied as a promising OER catalyst, are not stable in acidic or alkaline media for long-term operations. Simultaneous stabilization of high-surface-area Co₃O₄ and improvement in its electrocatalytic performance are highly desirable. We report here the use of atomically dispersed Bi atoms to not only stabilize 2D-Co₃O₄ nanosheets but also significantly improve their activity for OER in alkaline electrolyte. Our Bi/2D-Co₃O₄ catalyst possesses an OER activity ~250 times that of the commercial Co₃O₄ catalyst and much superior performance to the commercial IrO₂ and most of the previously reported OER catalysts. Quantitative measurements confirmed that for OER in 1 M KOH electrolyte the Bi/2D-Co₃O₄ catalyst was ~400 times more stable than the commercial IrO₂ catalyst. The presence of stable high-valent Bi and the formation of distinctive (Bi-O-Co)_n species are proposed to account for both the activity enhancement and the extreme stability of our Bi/2D-Co₃O₄ OER catalyst.

Dongyao Wang

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