Enhanced Hydrogen Evolution Reaction over Co Nanoparticles Embedded N-Doped Carbon Nanotubes Electrocatalyst with Zn as an Accelerant.

The rational design for transition metals-based carbon nano-materials as efficient electrocatalysts still remains a crucial challenge for economical electrochemical hydrogen production. Carbon nanotubes (CNTs) as attractive electrocatalysts are typically activated by non-metal dopant to promote catalytic performance. Metals doping or metal/non-metal co-doping of CNTs, however, are rarely explored. Herein, this work rationally designs bimetal oxide templates of ZnCo 2 O 4 for heterogeneously doping Zn and N into Co nanoparticles embedded carbon nanotubes (Co@Zn-N-CNTs). During the formation of CNTs, Zn atoms volatilize from ZnCo 2 O 4 and in situ dope into the carbon skeleton. In particular, owing to the low electronegativity of Zn, the electrons aptly transfer from Zn to carbon atoms, which generate a high electron density for the carbon layers and offer more preponderant catalytic sites for hydrogen reduction. The Co@Zn-N-CNTs catalyst exhibits enhanced hydrogen evolution reaction activity in 0.5 m H 2 SO 4 electrolyte, with a low onset potential of -20 mV versus RHE at 1 mA cm -2 , an overpotential of 67 mV at 10 mA cm -2 , a small Tafel slope of 52.1 mV dec -1 , and persistent long-term stability. This study provides brand-new insights into the utilization of Zn as electronic regulator and activity promoter toward the design of high-efficiency electrocatalysts.