Amorphous Intermediate Derivative from ZIF-67 and Its Outstanding Electrocatalytic Activity.

Increasing active sites is an effective method to enhance the catalytic activity of catalysts. Amorphous materials have attracted considerable attention in catalysis because of their abundant catalytic active sites. Herein, a series of derivatives is prepared via the low-temperature heat treatment of ZIF-67 hollow sphere at different temperatures. An intermediate product with an amorphous structure is formed during transformation from ZIF-67 to Co3 O4 nanocrystallines when ZIF-67 hollow sphere is heat treated at 260 °C for 3 h. The chemical composition of the amorphous derivative is similar to that of ZIF-67, and the carbon and nitrogen contents of the amorphous derivative are obviously higher than those of crystalline samples obtained at 270 °C or higher. As electrocatalysts for the oxygen evolution reaction (OER) and nonenzymatic glucose sensing, the amorphous derivative exhibits significantly better catalytic activity than crystalline Co3 O4 samples. The amorphous sample as an OER catalyst has a low overpotential of 352 mV at 10 mA cm-2 . The amorphous sample as an enzyme-free glucose sensing catalyst can provide a low detection limit of 3.9 × 10-6 m and a high sensitivity of 1074.22 µA mM-1 cm-2 .