Valence electronic engineering of superhydrophilic Dy-evoked Ni-MOF outperforming RuO2 for highly efficient electrocatalytic oxygen evolution

Abstract

Tackling the problem of poor conductivity and catalytic stability of pristine metal-organic frameworks (MOFs) is crucial to improve their oxygen evolution reaction (OER) performance. Herein, we introduce a novel strategy of dysprosium (Dy) doping, using the unique 4f orbitals of this rare earth element to enhance electrocatalytic activity of MOFs. Our method involves constructing Dy-doped Ni-MOF (Dy@Ni-MOF) nanoneedles on carbon cloth via a Dy-induced valence electronic perturbation approach. Experiments and density functional theory (DFT) calculations reveal that Dy doping can effectively modify the electronic structure of the Ni active centers and foster a strong electronic interaction between Ni and Dy. The resulting benefits include a reduced work function and a closer proximity of the d-band center to the Fermi level, which is conducive to improving electrical conductivity and promoting the adsorption of oxygen-containing intermediates. Furthermore, the Dy@Ni-MOF achieves superhydrophilicity, ensuring effective electrolyte contact and thus accelerating reaction kinetics. Ex-situ and in-situ analysis results manifest Dy2O3/NiOOH as the actual active species. Therefore, Dy@Ni-MOF shows impressive OER performance, significantly surpassing Ni-MOF. Besides, the overall water splitting device with Dy@Ni-MOF as an anode delivers a low cell voltage of 1.51 V at 10 mA cm−2 and demonstrates long-term stability for 100 h, positioning it as a promising substitute for precious metal catalysts.