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

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 H 3 PMo 12 O 40 @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/cm 2 ) in PBS and even as low as 570 mV (j = 10 mA/cm 2 ) in seawater. Besides, it also displays excellent catalytic performance for oxygen reduction (E 1/2 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. A multifunctional carbon-based electrocatalyst, PMA@ZIF-67-C-AT, was successfully prepared by carbonization and acid treatment of H 3 PMo 12 O 40 @ZIF-67 precursor. It not only exhibits excellent catalytic performance for ORR in alkaline solution, but also has efficient catalytic activity and stability for HER and OER actual seawater. • Multifunctional carbon-based catalyst derived from polyoxometalates and MOFs. • Efficient bifunctional catalyst for hydrogen and oxygen evolution in seawater. • Excellent ORR catalytic ability with a Tafel slope smaller than that of Pt/C. • The performance of catalyst is affected by active components and carbon matrix.