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

Abstract

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 ZnCo2 O4 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 ZnCo2 O4 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 offermore preponderant catalytic sites for hydrogen reduction. The Co@Zn-N-CNTs catalyst exhibits enhanced hydrogen evolution reaction activity in 0.5m H2 SO4 electrolyte, with a low onset potential of -20mV versus RHE at 1mA cm-2 , an overpotential of 67mV at 10mA cm-2 , a small Tafel slope of 52.1mV 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.