Gram-Scale production of Cu₃P-Cu₂O Janus nanoparticles into nitrogen and phosphorous doped porous carbon framework as bifunctional electrocatalysts for overall water splitting

Transition metal phosphides and oxides are heralded as inexpensive alternatives to precious metal catalysts for the electrochemical hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. Combing both transition metal phosphides and oxides into one catalyst system can generate a bifunctional electrocatalyst for overall water splitting. Still, the synthesis of such a catalyst has always been very challenging. Herein, we report the synthesis of Cu₃P-Cu₂O Janus bifunctional catalysts into a N, P co-doped 3D hierarchically porous carbon framework (Cu₃P-Cu₂O/NPC). Simple carbonization of Cu²⁺-containing ion-exchange resins with KOH make hundred-gram scale production of this superior catalyst possible. The Janus Cu₃P-Cu₂O heterostructure within a N, P-doped hierarchically porous carbon framework provides increased mass transport, enhanced electrocatalytic activity, and promoted cycling durability. As an electrocatalyst, the designed Cu₃P-Cu₂O/NPC delivers superior bifunctional activity for both the HER and OER in 1 M KOH, including extremely low overpotentials (138 mV for HER and 286 mV for OER) to reach a current density of 10 mA cm⁻² and small Tafel slopes (62.64 mV dec^-1 for HER and 79.02 mV dec^-1 for OER). More impressively, the Cu₃P-Cu₂O/NPC-assembled electrolyzer needs drive voltages of only approximately 1.57 and 1.81 V to achieve current densities of 10 and 50 mV cm⁻², respectively, demonstrating a superior electrocatalytic activity compared to the state-of-the-art electrolyzer (Pt/C || RuO₂/C), and exhibits ultrahigh stability over a week of continuous overall water splitting reaction. This work highlights the significance of nanoengineering on the production of highly efficient electrocatalysts and provides a promising bifunctional electrocatalyst for future industrial implementation.