Cr‐Doped FeNi–P Nanoparticles Encapsulated into N‐Doped Carbon Nanotube as a Robust Bifunctional Catalyst for Efficient Overall Water Splitting

: Exploring high-efficiency, stable, and cost-effective bifunctional electrocatalysts for overall water splitting is greatly desirable and challenging. Herein, a newly designed hybrid catalyst with Cr-doped FeNi-P nanoparticles encapsulated into N-doped carbon nanotubes (Cr-doped FeNi-P/NCN) with unprecedented electrocatalytic activity is developed by a simple one-step heating treatment. The as-synthesized Cr-doped FeNi-P/NCN with moderate Cr doping exhibits admirable oxygen evolution reaction and hydrogen evolution reaction activities with overpotentials of 240 and 190 mV to reach a current density of 10 mA cm-2 in 1 m KOH solution. When used in overall water splitting as a bifunctional catalyst, it needs only 1.50 V to give a current density of 10 mA cm-2 , which is superior to its typically integrated Pt/C and RuO2 counterparts (1.54 V @ 10 mA cm-2 ). Density functional theory calculation confirms that Cr doping into a FeNi-host can effectively alter the relative Gibbs adsorption energy and reduces the theoretical overpotential. Additionally, the synergetic effects between Cr-doped FeNi-P nanoparticles and NCNs are regarded as significant contributors to accelerate charge transfer and promote electrocatalytic activity in hybrid catalysts.