Studying the Effect of CuCo 2 S 4 Morphology on the Oxygen Evolution Reaction using a Flexible Carbon Cloth Substrate

The different morphologies of CuCo 2 S 4 have a significant effect on the electrocatalytic activity. However, the reasons for the activity difference of catalysts with multiple morphologies have raised little concern. Herein, we put forward the concept of “active edge perimeter” to evaluate the relative number of active sites. The morphologies are regulated by arranging NH 4 F from 0 to 3 mmol to prepare microsheet, tight‐binding microsheet, hybrid microsheet/wire, long microwire and short wire morphologies. The long‐perimeter microsheets can achieve a low Tafel slope (89 mV dec −1 ) and overpotential (283 mV) to reach a current density of 20 mA cm −2 for the oxygen evolution reaction. For microsheets, the charge‐transfer resistance is well under 50 % of the average values. The electrochemical surface area is above average area, owing to the high double‐layer capacitance. Therefore, for two‐dimensional microsheets, the long active perimeter is the main reason it ensures the high activity required for hierarchical catalysts.