Synergistic construction of an iron nitride embedded graphitic carbon nitride heterostructure electrocatalyst as a potential candidate to accelerate overall water electrolysis

Abstract

The development of efficient bifunctional electrocatalysts is a central part of electrochemical energy conversion systems. Herein, we have reported a new avenue for cost-effective construction of iron nitride embedded graphitic carbon nitride (Fe₃N@CN-x) electrocatalysts derived from potassium ferrocyanide via solid-state pyrolysis. At an optimized temperature, the synergistic construction of an iron nitride embedded graphitic carbon nitride Fe₃N@CN-700 heterostructured electrocatalyst has explored potential bifunctional activity towards overall water splitting. The constructed Fe₃N@CN-700 heterostructure offered maximum atom utility and expanded active surface area for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The optimized Fe₃N@CN-700 catalyst exhibits an overpotential of as low as 281 mV for the OER and 133 mV for the HER at a geometrical current density of 10 mA cm⁻². Moreover, a full-cell water electrolyzer assembled with a non-precious electrode pair of Fe₃N@CN-700‖Fe₃N@CN-700 required only an applied bias of 1.64 V, which is nearly equal to that required by state-of-the-art electrode pairs Pt–C‖IrO₂ (1.62 V at 10 mA cm⁻²). The Fe₃N@CN-700 heterostructure catalyst exhibits outstanding catalytic stability over 170 h for the OER, HER and overall water splitting. Renewable energy-based hydrogen production has been successfully demonstrated with the solar assisted full cell water electrolyzer at 1.64 V. The current study introduced a new approach to designing non-precious metal nitride and graphitic carbon nitride based catalysts for scale-up energy conversions.