A high-efficiency urea electrolysis catalyst: Sulfur-doped lignin-derived carbon-encapsulated NiCo@MoO2 with triphasic interface and superhydrophilic/superaerophobic surfaces

To address the intrinsic activity and stability limitations of nickel-based heterojunction catalysts in the urea oxidation process (UOR) and the hydrogen evolution reaction (HER) under strongly alkaline conditions, a sulfur-doped lignin-derived carbon-encapsulated NiCo@MoO 2 heterostructure (NiCo@MoO 2 /SC) as a bifunctional catalyst is engineered. The physical properties, electrochemical characterization, and simulation results demonstrate that the built-in electric field at the triphasic interface synergistically optimizes the electronic structure of NiCo@MoO 2 /SC, enhancing the UOR process by rapidly generating the NiOOH active site. Meanwhile, charge redistribution in this heterostructure activates ortho‑carbon in the sulfur-doped carbon as HER active sites, significantly enhancing the HER process. Consequently, NiCo@MoO 2 /SC delivers exceptional catalytic activity in both UOR ( E 10/500/1000  = 1.26/1.38/1.40 V) and HER ( E −10/−500/−1000  = −27/−216/−288 mV). Besides, the carbon-encapsulated strategy improves corrosion resistance to enhance chemical stability, while the micro-nano array structure with the superhydrophilic/superaerophobic surfaces facilitates gas-liquid desorption to boost mechanical stability, enabling stable operation at ±1000 mA cm −2 for 100 h, even in a two-electrode system. This study proposes a viable approach to designing efficiency bifunctional electrocatalysts for urea electrolysis, while broadening the prospects of high-value utilization in biomass-derived carbon materials.