Conformally Coated Nickel Phosphide on 3D, Ordered Nanoporous Nickel for Highly Active and Durable Hydrogen Evolution

Microstructuring is an effective strategy to manipulate the active sites of electrocatalysts to improve their performance, but there are few reports that focus on continuous three-dimensional (3D) nanopatterning. Herein, 3D continuous nanopatterns with a pore size of 100 nm of nickel phosphide are fabricated and evaluated for acidic electrocatalytic hydrogen evolution reaction (HER). The 3D continuous nanopatterned catalyst requires a minimum overpotential of 101 mV to achieve a current density of 10 mA·cm–2 and a Tafel slope of 60 mV·dec–1, which outperforms most electrocatalysts based on transition metal derivatives. The turnover frequency of nanopatterns is 0.87 s–1 at an overpotential of 100 mV, which is very close to benchmark electrocatalyst Pt/C (0.90 s–1). This nanopatterned catalyst also displays superior durability: up to 250 h of continuous operation without any decay. Experimental analysis suggests that nanopatterns of active materials expose more active sites, and high curvature (r c < 100 nm) of nanopores allows fast discharge of gas bubbles for fast and efficient production of H2 with high stability. Continuous, ordered nickel nanonetworks coated by the nickel phosphide also allow fast transportation of ions to facilitate the H* desorption process, contributing to improved kinetics for outstanding HER activity.