Oxygen electrocatalysis is of great importance for many energy storage and conversion technologies including fuel cells, metal-air batteries and water electrolysis. Replacing noble metal-based electrocatalysts with highly efficient and inexpensive non-noble metal based oxygen electrocatalysts is critical for the practical applications of these technologies. Here we report a general approach for the synthesis of hollow frameworks of nitrogen-doped carbon nanotubes derived from metal-organic frameworks, which exhibit higher electrocatalytic activity and stability for oxygen reduction and evolution than commercial Pt/C electrocatalysts. The remarkable electrochemical properties are mainly attributed to the synergistic effect from chemical compositions and the robust hollow structure composed of interconnected crystalline nitrogen-doped carbon nanotubes. The presented strategy for controlled design and synthesis of metal-organic framework-derived functional nanomaterials offers prospects in developing highly active electrocatalysts in electrochemical energy devices.

This review summarizes recent research progress and perspectives on noble-metal-free bifunctional heterogeneous electrocatalysts towards hydrogen and oxygen evolution reactions in overall water splitting.

Hydrogen is expected to play a major role in the development of sustainable energy and environment. Electrocatalytic hydrogen evolution reaction (HER) is known as an efficient method for large-scale hydrogen production, and in this electrochemical process, efficient and low-cost electrocatalysts are indispensable. Recent advances have revealed that nanostructured molybdenum sulfides (MoSx) would be promising alternatives to Pt for the electrochemical generation of hydrogen from water. In this review, we focus on the recent progress on MoSx-based materials as electrocatalysts toward the HER under acidic condition. Moreover, future research scope and important challenges emerging from MoSx nanostructures are discussed toward the development of more advanced and efficient electrocatalysts for HER.