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/CoS_<i>x</i>) employing hydrothermal sulfidation. Benefiting from the CeS/CoS_<i>x</i> architecturally engineered hollow polyhedral nanocage structure and strong electronic interaction between CeS and CoS_<i>x</i>, the composite catalyst demonstrates significantly accelerated electron transfer kinetics and outstanding catalytic activity. In 1.0 M KOH, CeS/CoS_<i>x</i> 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/CoS_<i>x</i>||CeS/CoS_<i>x</i> 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.