Enhanced Electrocatalytic Performance of Erbium-Incorporated Nickel-Based Metal–Organic Frameworks for Water Splitting

Developing cost-effective and highly efficient electrocatalysts for water splitting has remained a significant challenge in recent research. In this study, we report a facile approach to synthesize nickel–1,2-benzenedicarboxylic acid (H₂BDC) metal–organic frameworks (Ni–BDC MOFs) and rare-earth erbium (Er) ion-incorporated Ni–BDC MOFs. These MOFs are employed as electrocatalysts for oxygen evolution reactions (OERs) and hydrogen evolution reactions (HERs). Remarkably, a lower concentration of Er demonstrated excellent OER performance, while a higher Er incorporation was conducive to HER performance. For OER, a current density of 100 mA cm^–2 was achieved at an overpotential of 420 mV in the case of Er_0.5Ni–BDC MOF. Meanwhile, Er–Ni–BDC MOF exhibited a current density of 10 mA cm^–2 at 270 mV for HER. The Er-incorporated Ni–BDC MOFs exhibited prolonged electrochemical durability with a retention rate of 87% for OER and 90% for HER. The electrocatalytic performance of Er-incorporated Ni–BDC MOFs was found to be higher than that of the pure Ni–BDC and Er–BDC MOFs. The improvement in the electrocatalytic performance of Ni–BDC MOFs upon Er incorporation was attributed to the synergistic effects of the Ni and Er sites, where Er contributes to modifying the electronic states of the Ni sites, thereby enhancing the OER and HER activity. The demonstrated strategy of augmenting HER and OER activity in Ni-MOF through the incorporation of rare-earth ions opens up new avenues for designing MOF catalysts tailored for industrial OER and HER applications.