Unraveling Surface Reconstruction of MOF-Derived La, P-Co3O4 for Energy-Efficient Water and Urea Electrolysis.

Abstract

Constructing robust electrocatalysts and shedding light on the processes of surface reconstruction is crucial for sustained hydrogen production and a deeper understanding of catalytic behavior. Here, a novel ZIF-67-derived lanthanum- and phosphorus-co-doped Co₃O₄ catalyst (La, P-Co₃O₄) has been reported. X-ray absorption spectroscopy (XAS) confirms that the La and P co-doping reduces the coordination number (CN), improves oxygen vacancies (O_v), and leads to lattice distortion. Soft XAS confirms that Co²⁺ exists predominantly in La, P-Co₃O₄ than in Co₃O₄. Investigation of surface reconstruction with in situ Raman spectroscopy_, revealing that La, P-Co₃O₄ reconstructs earlier into catalytically active γ-CoOOH during the oxygen evolution reaction (OER) process. As a result, La, P-Co₃O₄ exhibits commendable electrocatalytic performance with minimal overpotentials of 351 mV for the OER, 222 mV for the hydrogen evolution reaction (HER), and 1.46 V for the urea oxidation reaction (UOR) to achieve a current density of 50 mA cm^-2. A two-electrode electrolyzer using La, P-Co₃O₄ as anode and cathode, achieving 19.4% energy savings during urea electrolysis compared to overall water electrolysis while maintaining stability for 72 h. This study provides a new perspective for understanding the mechanism and co-doping impact on the physicochemical properties of spinel Co₃O₄ for sustainable energy conversion.