Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage, in which robust electrocatalysts for efficient oxygen evolution play crucial roles for its realization. However, so far electrocatalysts with long-term stability remain elusive owing to harsh conditions during the oxygen evolution reaction (OER). In this study, we demonstrate that single-crystal Co3O4 nanocube underlay a thin CoO layer results in a high-performance, high-stability OER electrocatalyst. This electrocatalyst exhibits strong mechanical strength and defect-free substrates with CoO uniformly covering over single-crystal Co3O4 nanostructures. In-situ X-ray diffraction method was developed to observe a strong correlation between the initialization of the O2 evolution and the transformation of the CoO layer into active metal oxyhydroxide catalysts. The lattice of the skin layer thus self-adapt to the structures of the active species, enabling a reversible facile structure change that facilitates the chemical reactions (e.g., OER) and thus the formation of active species without breaking the scaffold of the electrocatalysts (e.g., Co3O4 nanocubes). The Co3O4@CoO single-crystal nanocube electrode exhibited stable, continuous oxygen evolution for more than 1000 hours with ~100% Faradaic efficiency at various current densities. This robust stability was attributed to the complementary nature of defect-free single-crystal electrocatalysts and the self-adapting CoO layer that could sustain the frequent volume changes generated from the harsh anodizing process. These results provide significant progress towards the understanding of the active intermediates on catalysts’ surface, and the development of a novel strategy to utilize a self-adapting layer for reliable electrocatalysts for oxygen evolution.

Self-adapting layer of robust single-crystal earth-abundant nanoparticles catalyzing oxygen evolution

249th National Meeting (2015)

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