Synergetic Modulation of Electronic Properties of Cobalt Oxide via "Tb" Single Atom for Uphill Urea and Water Electrolysis.

Exploring single-atom (SA) catalysts in hybrid urea-assisted water electrolysis offers a viable alternative to both Hydrogen (H) generation and polluted water treatment. However, the unfavorable electronic stabilization, low SA content, intrinsically slow kinetics, and imbalanced adsorption-desorption steps are the bottleneck for its scale-up implementation. Herein, a rare-earth Terbium single atom (Tb) is topologically stabilized on defect-rich CoO (Tb@d-CoO) by Tb─O co-ordination for urea oxidation reaction (UOR) and H evolution reaction (HER). Benefitting from the strong Tb interaction with the d-CoO the Tb@d-CoO achieves a 10 mA cm current density at 1.27 V and -35 mV for UOR and HER, respectively. Remarkably, when Tb@d-CoO is applied as a bi-functional catalyst in a two-electrode system, it merely requires 1.22 V to acquire 10 mA cm with excellent operational stability for 100 h. The hybrid electrolyzer can be successfully empowered by the triboelectric nanogenerator, AA battery, and solar panel with a nominal potential of 1.5 V. The mechanistic investigation predicts "Tb" insertion in d-CoO lowered the potential determining step, attributed to balanced reaction energetics for adsorption-desorption of intermediates and favorable charge transfer characteristics for UOR. This work offers a new paradigm to explore the catalytic properties of rare-earth "f-block" elements to create advanced electrocatalysts via structural modulation.