Assembled cobalt phosphide nanoparticles on carbon nanofibers as a bifunctional catalyst for hydrogen evolution reaction and oxygen evolution reaction

Abstract

The search for efficient and stable bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for the practical application of water splitting. Although transition metal-based phosphide catalysts have been widely studied as effective catalysts for the HER and OER, their catalytic applications are significantly limited by low electrical conductivity and the agglomeration effect. Herein we report a highly active electrocatalyst for HER and OER comprising CoP nanoparticles embedded in CNT-grafted carbon nanofibers (CNF@CoP-CNTs) obtained by the pyrolysis of a cobalt metal–organic framework (ZIF-67) in a reductive H₂ atmosphere and subsequent adjustable phosphating process. The optimized CNF@CoP-CNTs showed excellent HER and OER performance, evidenced by the small overpotentials of 65 mV @ 10 mA cm⁻² for HER and 367 mV @ 50 mA cm⁻² for OER. Remarkably, the CNF@CoP-CNTs can also display excellent long-term stability for more than 48 h for the OER test in an alkaline medium. In short, this research demonstrates that CNF@CoP-CNTs with a hierarchical structure could be a potential electroactive material in advanced electrocatalysts systems.