A 'point-line-point' hybrid electrocatalyst for bi-functional catalysis of oxygen evolution and reduction reactions

Abstract

Both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) hold the core position in various sustainable energy systems. Attributed to their sluggish kinetics, the principle and concept to achieve efficient electrocatalysts for a sustainable catalytic process, especially bi-functional electrocatalysts with abundant active centers and 3D conductive scaffolds for both OER and ORR, are strongly considered. In this contribution, rather than physically mixing active catalyst flakes with conductive fillers, a hybrid electrocatalyst with ‘active point–conductive line–active point’ connections was proposed and validated. As a proof-of-concept, Co-based active sites embedded on layered double oxide (LDO) substrates interlinked with carbon nanotubes (CNTs) were realized and exhibited a superior bi-functional activity for both OER and ORR in an alkaline electrolyte. The LDO/CNT hybrids catalyzed the OER to reach 10.0 mA cm−2 at 1.64 V vs. RHE, and the ORR to reach 3.0 mA cm−2 at 0.65 V vs. RHE, with a potential gap of 0.99 V. Such model catalysts of LDO/CNT hybrids even delivered a better bi-functional performance than routine noble metal catalysts (e.g. Pt/C and IrO2). The novel strategy of combining metal compounds and carbon nanomaterials through ‘point–line–point’ configurations can be applied to other hierarchical composites with multi-building blocks, aiming at promising applications in energy storage and environmental protection.