Phosphorized CoNi2S4 Yolk‐Shell Spheres for Highly Efficient Hydrogen Production via Water and Urea Electrolysis

Abstract Exploring earth‐abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi 2 S 4 yolk‐shell spheres (P‐CoNi 2 S 4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas‐phase phosphorization strategy. Benefiting from the strengthened Ni 3+ /Ni 2+ couple, enhanced electronic conductivity, and hollow structure, the P‐CoNi 2 S 4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of −0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm −2 , respectively. Remarkably, when used as the anode and cathode simultaneously, the P‐CoNi 2 S 4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm −2 with excellent durability for 100 h, outperforming most of the reported nickel‐based sulfides and even noble‐metal‐based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea‐rich wastewater treatment.