Three birds with one stone: Ni–MoN nano-heterostructures encapsulated in NCNTs for efficient hydrogen production via overall water splitting and urea electrolysis†

Development of efficient multifunctional electrocatalysts for hydrogen production from overall water splitting (OWS) and urea electrolysis (UE) is highly desired yet challenging. Herein, Ni–MoN nano-heterostructures encapsulated in NCNTs have been successfully fabricated on Cu foam (NMN@NC/CF), which exhibits excellent trifunctional catalytic activity toward the hydrogen evolution reaction (HER, η_10, 1200 = 69, 265 mV), oxygen evolution reaction (OER, η₁₀ = 191 mV) and urea oxidation reaction (UOR, E_10, 500 = 1.316, 1.450 V), outperforming noble metal-based catalysts due to its unique structure and intrinsic catalytic capability. Furthermore, a two-electrode electrolyzer using NMN@NC/CF as both the cathode and anode needs a much lower voltage of 1.376 V for UE than the value of 1.521 V for OWS to reach 10 mA cm⁻², and it can remain stable over 100 h during continuous UE operation at 500 mA cm⁻², demonstrating great promise for simultaneous energy-saving hydrogen production and remediation of urea-containing wastewater.