Synergistic effect of three-dimensional cobalt diselenide/carbon nanotube arrays composites for enhanced hydrogen evolution reaction

Highlights: • CoSe₂/CNTAs composite was synthesized via a microwave-thermal treatment-selenization method. • Such a composite shows the synergistic effect of CoSe₂ nanoparticles and CNTAs with well-ordered conductive paths and aligned intertube spacing. • The CoSe₂/CNTAs composite exhibits a low Tafel slope and a small overpotential at a high current density. Three-dimensional CoSe₂/carbon nanotube arrays (CoSe₂/CNTAs) composite with optimized morphology has been synthesized through a microwave-thermal treatment-selenization method. The CoSe₂ nanoparticles with an average size of ∼25 nm are anchored uniformly on the surface of CNTAs. The CoSe₂/CNTAs composite exhibits excellent hydrogen evolution reaction (HER) performance in an acidic electrolyte with a low Tafel slope of 36.7 mV/dec, a potential of −204 mV vs RHE at 10 mA/cm² and especially a low overpotential of 229 mV at a high current density of 100 mA/cm². The high electrocatalytic activity can be achieved by the synergistic effect of CoSe₂ nanoparticles and CNTAs. The CoSe₂ catalyst particles with nanoscale size provide abundant active sites for HER. The CNT arrays possess well-ordered 1D conductive paths, providing a fluent charge transport channel for CoSe₂ catalyst nanoparticles and external electrodes. Meanwhile, CNTAs with aligned intertube spacing can provide sufficient space for the penetration of electrolyte, rapid transport of ions (H⁺) and release of produced H₂. Thus even at a high current density, the hydrogen evolution reaction can proceed smoothly.