Nickel nanoparticles encapsulated by nitrogen-doped bamboo-shaped carbon nanotubes with a high-level doping: A boosting electrocatalyst for alkaline hydrogen evolution

The development of highly active and stable alkaline hydrogen evolution electrocatalysts is highly desired in the field of clean energy. Herein, we chose urea and nickel chloride as precursors, and synthesized metallic Ni nanoparticles encapsulated by nitrogen-doped bamboo-shaped carbon nanotubes through one-pot calcination at low temperature (550 degrees C). Along with the increase in the amount of Ni salt, the electrocatalyst support has undergone a transformation from polymeric carbon nitride to nitrogen-doped carbon, and the charge transport ability and electrochemical active surface area of the electrocatalysts have been significantly improved. For the optimized Ni/NC-0.35 electrocatalyst with 13.42 wt% nitrogen-doping level, the overpotential at cathodic current density of 10 mA cm-2 is 133 mV (vs. RHE) in alkaline electrolyte, the corresponding Tafel slope is 109 mV dec-1, and there is no significant decrease in hydrogen evolution activity after 16 h. The boosting activity can be attributed to the synergistic effect of the mixed phase Ni nanoparticles, the high nitrogen-doping level and the bamboo-shaped carbon nanotube structure towards the alkaline hydrogen evolution reaction. This work provides a new way for the design of high-activity alkaline hydrogen evolution electrocatalysts and the facile synthesis of high nitrogen-doping carbon-coated metal nanoparticle catalysts.