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: alpha-Co(OH)(2) with both Co-Td(2+) and Co-Oh(2+) Oh sites and beta-Co(OH)(2) with Co-Oh(2+) sites. Electrochemical characterization reveals that alpha-Co(OH)(2) is more active than beta-Co(OH)(2) towards OER. The better activity can be attributed to the presence of Co-Td(2+) sites in alpha-Co(OH)(2), which are more active than Co-Oh(2+) sites. Our finding clarifies the contribution of the two catalytic sites and helps future rational design of high-performance OER electrocatalysts.