Electrochemical and Solvothermal Syntheses of HKUST-1 Metal Organic Frameworks and Comparison of their Performances as Electrocatalyst for Oxygen Reduction Reaction

In this study for the first time, the electrocatalytic performance of an electrochemically synthesized metal–organic framework (MOF) was compared with a solvothermally synthesized MOF. HKUST-1 MOF was synthesized by the electrochemical method at room temperature and very short time. Then, its performance as an electrocatalyst for oxygen reduction reaction (ORR) was studied in 0.5 M H2SO4, phosphate buffer 6 (PBS6) and 0.1 M NaOH solutions, among which the best result was obtained in PBS6. At the optimum condition the ORR was compared with a HKUST-1 synthesized by a common solvothermal method (at very longer time and higher temperature and pressure). ORR peak currents on glassy carbon electrode (GCE), solvothermally synthesized MOF (STMOFGCE), and electrochemically synthesized MOF (ECMOF-GCE) were 0.8, 8.1 and 29.6 mA. cm-2 respectively, and ORR peak potentials (Ep) were -0.83, -0.11 and -0.13 V, respectively. In comparing the ECMOF-GCE and STMOF-GCE, the Ep is almost the same, but the peak current density for the former is very greater and its ORR onset potential is considerably more positive than STMOF-GCE, which means the ORR is thermodynamically easier on ECMOF-GCE.