Phase-controllable synthesis of cobalt hydroxide for electrocatalytic oxygen evolution.

Identification of active sites for oxygen evolution reaction (OER) plays a key role in the design and fabrication of high-performance cobalt-based electrocatalysts. Herein, we report the synthesis of two types of two-dimensional monometallic cobalt hydroxide nanoplates in aqueous solution for OER: α-Co(OH) with both Co and Co sites and β-Co(OH) with Co sites. Electrochemical characterization reveals that α-Co(OH) is more active than β-Co(OH) towards OER. The better activity can be attributed to the presence of Co sites in α-Co(OH), which are more active than Co sites. Our finding clarifies the contribution of the two catalytic sites and helps future rational design of high-performance OER electrocatalysts.