Hierarchical porous NiFe-P@NC as an efficient electrocatalyst for alkaline hydrogen production and seawater electrolysis at high current density

Economical, efficient and stable transition-metal electrocatalysts are considered great candidatures for replacing noble-metal materials for alkaline hydrogen production. Hence, corrosion engineering and mild phosphating processes were adopted to construct NiFe phosphide encapsulated in nitrogen-doped carbon (NiFe-P@NC). The latter presented a hierarchical morphology with an interconnected three-dimensional porous structure. The unique NiFe-P@NC presented excellent hydrogen evolution reaction (HER) performance with an overpotential of 40 mV at 10 mA cm(-2) along with excellent stability in KOH solution (1 M). Notably, NiFe-P@NC required low overpotentials of 149 mV and 280 mV to afford 100 mA cm(-2) for HER and oxygen evolution reaction (OER) performance in KOH (1 M) + seawater electrolyte, respectively. Furthermore, as a remarkable bifunctional electrocatalyst, the assembled NiFe-P@NC || NiFe-P@NC electrolyzer with low cell voltages of 1.77 V and 1.93 V could drive 100 mA cm(-2) and 500 mA cm(-2) in alkaline seawater electrolyte. Remarkably, a water-splitting device could be actuated efficiently by sustainable energies to facilitate a source of hydrogen energy.

Automated summary

Economical, efficient and stable transition-metal electrocatalysts have been developed to replace noble-metal materials for alkaline hydrogen production. A new NiFe phosphide encapsulated in nitrogen-doped carbon (NiFe-P@NC) was constructed using corrosion engineering and mild phosphating processes. NiFe-P@NC exhibited excellent hydrogen evolution reaction (HER) performance and stability in KOH solution (1 M), and low overpotentials for HER and oxygen evolution reaction (OER) in KOH (1 M) + seawater electrolyte. Additionally, a bifunctional electrolyzer assembled with NiFe-P@NC could drive high current densities in alkaline seawater electrolyte.