MOF-Derived Ce–Co–S Hollow Polyhedral Nanocages via Dual-MOF Templating for Enhanced Bifunctional Overall Water Splitting

Metal–organic frameworks (MOFs) have gained widespread recognition as versatile catalyst precursors owing to their unique structural merits and straightforward synthetic accessibility. Herein, the UiO-66(Ce)/ZIF-67 composite MOF precursor was constructed through a hybridization strategy, and subsequently transformed into a nonprecious metal sulfide catalyst (denoted as CeS/CoSx) employing hydrothermal sulfidation. Benefiting from the CeS/CoSx architecturally engineered hollow polyhedral nanocage structure and strong electronic interaction between CeS and CoSx, the composite catalyst demonstrates significantly accelerated electron transfer kinetics and outstanding catalytic activity. In 1.0 M KOH, CeS/CoSx only necessitates an overpotential of 143 mV to achieve a current density of 10 mA cm–2 for the hydrogen evolution reaction (HER). Regarding the oxygen evolution reaction (OER), overpotentials of 250 and 291 mV were required to attain current densities of 10 and 50 mA cm–2, respectively. Remarkably, the assembled CeS/CoSx||CeS/CoSx two-electrode overall water splitting system requires only 1.60 V to achieve a current density of 10 mA cm–2. Moreover, during the 40 h continuous electrolysis test, the potential fluctuation remained within 1%. This study provides an effective strategy for designing high-performance, dual-MOF-derived sulfide composite bifunctional electrocatalysts.