Polyoxometalate@ZIF-67 derived carbon-based catalyst for efficient electrochemical overall seawater splitting and oxygen reduction

Abstract

Electrochemical water splitting, metal-air batteries and fuel cells are the representatives of energy storage/conversion technology, which can solve the shortage of traditional fossil energy and environmental issues. However, under neutral conditions, especially in natural seawater, there is still a lack of catalysts with efficient catalytic activity and stability, which hinders the development of hydrogen production. We herein designed a facile strategy to fabricate an efficient and stable multifunctional carbon-based electrocatalyst, PMA@ZIF-67-C-AT, by carbonization and acid treatment of H3PMo12O40@ZIF-67 precursor. It not only performs good catalytic activity for oxygen evolution in 0.2 M phosphate buffer solution (PBS) and actual seawater, but also exhibits hydrogen evolution overpotential of 650 mV (j = 3 mA/cm2) in PBS and even as low as 570 mV (j = 10 mA/cm2) in seawater. Besides, it also displays excellent catalytic performance for oxygen reduction (E1/2 at 0.83 V and the Tafel slope of 63 mV/dec). By investigating the composition and morphology of the materials, it was found that acid treatment changed the active components and carbon matrix of the catalysts, thus affecting the catalytic performance.