Self-assembled globular clusters-like cobalt hexacyanoferrate/carbon nanotubes hybrid as efficient nonprecious electrocatalyst for oxygen evolution reaction

For the first time, a novel of self-assembled globular clusters-like cobalt hexacyanoferrate/carbon nanotubes electrocatalyst has been synthesized by a facile one-pot chemical co-precipitation method. Compared to bare cobalt hexacyanoferrate with higher onset overpotential of 296 mV vs. RHE, a larger Tafel slope of 107.27 mV dec(-1) and higher overpotential of 411 mV at 10 mA cm(-2) for OER, the optimized cobalt hexacyanoferrate/carbon nanotubes hybrid exhibits a much lower Tafel slope of 62.43 mV dec(-1) and smaller onset overpotential of 152 mV, and its overpotential at 10 mA cm(-2) is only 274 mV. Most importantly, at a fixed overpotential of 400 mV, cobalt hexacyanoferrate/carbon nanotubes hybrid with 20 mg carbon nanotubes delivers a large current density of 95.02 mA cm(-2), which is over ten times than that of bare cobalt hexacyanoferrate (8.52 mA cm(-2)). The dramatically enhanced OER performances are mainly assigned to the unique globular clusters-like structure and the good synergistic effect between cobalt hexacyanoferrate nanoparticles and highly conductive carbon nanotubes skeleton, leading to producing the higher electrochemical active surface area and much lower impedance. This work provides a simple strategy to rationally design and synthesize transition metal hexacyanoferrate-based catalysts as highly efficient nonprecious electrocatalysts for OER.