A novel Co-based MOF/Pd composite: synergy of charge-transfer towards the electrocatalytic oxygen evolution reaction

Abstract

A novel Co-based MOF/Pd composite (LEEL-037/Pd–C) was synthesized and evaluated towards the oxygen evolution reaction (OER) in alkaline medium. The composites' formation improved the surface-electrochemistry of Pd nanoparticles to carry out the OER. XRD and TEM reveal a crystallite size increase and a crystal lattice distortion for LEEL-037/Pd–C composites. LEEL-037/Pd–C samples containing 25 and 50 wt% LEEL-037 show an improvement of the electrochemical surface area (ECSA) due to a structural interaction that enhances the electrocatalytic activity of bare materials. Based on the electrochemical and XPS results, a charge-transfer mechanism is proposed to explain an improvement of the OH⁻adsorption degree on the LEEL-037/Pd–C composites. Since OER activity in alkaline medium is directly related to the initial OH⁻adsorption process, LEEL-037/Pd–C composites enhance their OER electrocatalytic activity. The composite LEEL-037(25)/Pd–C(75) exhibited the lowest operational potential to reach 10 mA cm⁻² (1.66 V); additionally, the EIS measurements show that it exhibited the lowest charge-transfer resistance. Insights into this reaction mechanism and charge-transfer process become a promising strategy to tailor the electrochemical activity towards the OER.