Self-driven Ru-modified NiFe MOF nanosheet as multifunctional electrocatalyst for boosting water and urea electrolysis.

Ru-modified NiFe MOF nanosheet array was elaborately designed via self-driven galvanic replacement reaction (GRR), which exhibits dramatically enhanced HER, OER and UOR catalytic property as a multifunctional electrocatalyst. [Display omitted] • Ru-modified NiFe MOF nanosheet array was designed via self-driven galvanic replacement reaction. • Enhanced catalytic potency benefitted from spontaneous electronic reconstruction in the interface. • The Ru-NiFe- x /NF are endowed with richer high-valence Ni active species. • The Ru-NiFe- x /NF can operate as multifunctional electrocatalyst with high current density. Urea electro-oxidation reaction (UOR) has been a promising strategy to replace oxygen evolution reaction (OER) by urea-mediated water splitting for hydrogen production. Naturally, rational design of high-efficiency and multifunctional electrocatalyst towards UOR and hydrogen evolution reaction (HER) is of vital significance, but still a grand challenge. Herein, an innovative 3D Ru-modified NiFe metal-organic framework (MOF) nanoflake array on Ni foam (Ru-NiFe- x /NF) was elaborately designed via spontaneous galvanic replacement reaction (GRR). Notably, the adsorption capability of intermediate species (H*) of catalyst is significantly optimized by Ru modification. Meanwhile, rich high-valence Ni active species can be acquired by self-driven electronic reconstruction in the interface, then dramatically accelerating the electrolysis of water and urea. Remarkably, the optimized Ru-NiFe-③/NF (1.6 at% of Ru) only requires the overpotential of 90 and 310 mV to attain 100 mA cm−2 toward HER and OER in alkaline electrolyte, respectively. Impressively, an ultralow voltage of 1.47 V is required for Ru-NiFe-③/NF to deliver a current density of 100 mA cm−2 in urea-assisted electrolysis cell with superior stability, which is 190 mV lower than that of Pt/C-NF||RuO 2 /NF couple. This work is desired to explore a facile way to exploit environmentally-friendly energy by coupling hydrogen evolution with urea-rich sewage disposal. [ABSTRACT FROM AUTHOR]