Nanoparticles Embedded in MOFs with Surface Conductance Enhancement for Efficient Electrocatalytic Water Splitting

Three robust and highly efficient RuO2 nanoparticle–embedded metal–organic frameworks (MOFs), RuO2@Zn2M2(μ2–OH)2(BTMB)2 (M = Zn (1), Co (2), Ni (3)), were achieved as bifunctional electrocatalysts for comprehensive water splitting. The pristine low-conducting frameworks, Zn2M2(μ2–OH)2(BTMB)2, were transformed into high-conducting analogues through postsynthetic encapsulation of ∼1–2.26 wt % RuO2 nanoparticles via a sonochemical approach. Comprehensive characterization by PXRD, SEM, TEM, EDX, and TGA confirmed successful nanoparticle incorporation and framework integrity. The RuO2@MOFs demonstrated exceptional superhydrophobicity with contact angles of 173.0°, 171.5°, and 172.3°, notably higher than those of their pristine counterparts (155.5°, 159.3°, and 160.8°). The incorporation of RuO2 significantly enhanced the electrocatalytic performance, resulting low overpotentials for the hydrogen evolution reaction (HER) (125, 98, and 117 mV) and oxygen evolution reaction (OER) (490, 390, and 430 mV) with small Tafel slopes (78–64 mV dec–1 for HER; 138–113 mV dec–1 for OER) in 1 M KOH alkaline conditions. These results indicate a 4–6-fold improvement in activity compared to the pristine MOFs. Among the series, RuO2@Zn2Co2(μ2–OH)2(BTMB)2(2) displayed the best overall catalytic efficiency and long-term stability, retaining its activity for over 72 h under continuous operation. The superior performance arises from the synergistic combination of RuO2 strong conductivity nature and the bimetallic framework’s structural robustness, establishing these materials as promising and durable catalysts for efficient water splitting.