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Currently, there are still many limitations in the research of conductive metal-organic frameworks (MOFs) in the field of electrocatalysis. On the one hand, most MOFs have a solid construction, seriously hindering their mass transfer process. On the other hand, innate bonding is not conducive to the optimization of electronic structures and the excitation of intrinsic active sites. Therefore, external/internal dual-control of MOFs is urgently needed to break the shackles of their activity. Herein, the hollow RuCoCu-MOF/CF nanorods with tunable cavities are directionally constructed by a self-sacrificial template method. Benefiting from the exact morphological control and the unique Ru–O–Co bond bridge, RuCoCu-MOF/CF exhibits superior performances for alkaline hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). Surprisingly, a record-breaking voltage of 1.402 V drives a current density of 10 mA cm−2 for urea-assisted overall water splitting under alkaline conditions, greatly promoting the development of energy-efficient hydrogen production technology. This work firstly constructed the MOF-based self-supporting electrode with ultra-high urea-assisted hydrogen production and urea degradation performances via the dual controls of the cavity size and chemical bond bridge. This points out the direction for the development of unique integrated electrodes for both hydrogen production and decontamination. "External and internal dual-controls" strategy of the cavity size and chemical bridge construction in RuCoCu-MOF nanorod achieves bifunctional catalysis of urea-assisted energy-saving hydrogen production and urea decomposition. Surprisingly, the unique structure and the formation of the Ru–O–Co bond bridge make RuCoCu-MOF/CF only need a voltage of 1.402 V to reach a current density of 10 mA cm−2 in the energy-efficient HER||UOR electrolyzer, this excellent value represents the highest performance of overall water splitting under alkaline conditions. Besides, RuCoCu-MOF/CF also achieves 2.21 times higher HER activity than commercial Pt/C/CF and splendid UOR properties in the alkaline solution. [Display omitted] • The controllable cavity was constructed by the balance of dissolution-coordination and nucleation-growth processes. • The Ru–O–Co bond bridge as the electron channel optimizes the electronic configuration. • RuCoCu-MOF/CF achieves the record-breaking urea-assisted overall water splitting performance (V 10 = 1.402 V). • RuCoCu-MOF/CF achieves the ultra-low overpotential of 11.6 mV at η 10 for HER, which is better than that of Pt/C/CF. • The ultra-low onset potential of 1.32 V is displayed in RuCoCu-MOF for UOR. [ABSTRACT FROM AUTHOR]

Developing efficient, stable and ideal urea oxide (UOR) electrocatalyst is key to produce green hydrogen in an economical way. Herein, Ru doped three dimensional (3D) porous Ni 3 N spheres, with tannic acid (TA) and urea as the carbon and nitrogen resources, is synthesized via hydrothermal and low-temperature treated process (Ru–Ni 3 N@NC). The porous nanostructure of Ni 3 N and the nickel foam provide abundant active sites and channel during catalytic process. Moreover, Ru doping and rich defects favor to boost the reaction kinetics by optimizing the adsorption/desorption or dissociation of intermediates and reactants. The above advantages enable Ru–Ni 3 N@NC to have good bifunctional catalytic performance in alkaline media. Only 43 and 270 mV overpotentials are required for hydrogen evolution (HER) and oxygen evolution (OER) reactions to drive a current of 10 mA cm−2. Moreover, it also showed good electrocatalytic performance in neutral and alkaline seawater electrolytes for HER with 134 mV to drive 10 mA cm−2 and 83 mV to drive 100 mA cm−2, respectively. Remarkably, the as-designed Ru–Ni 3 N@NC also owns extraordinary catalytic activity and stability toward UOR. Moreover, using the synthesized Ru–Ni 3 N@NC nanomaterial as the anode and cathode of urea assisted water decomposition, a small potential of 1.41 V was required to reach 10 mA cm−2. It can also be powered by sustainable energy sources such as wind, solar and thermal energies. In order to make better use of the earth's abundant resources, this work provides a new way to develop multi-functional green electrocatalysts. [Display omitted] • The synthesized electrocatalyst exhibits porous specific sphere morphology to exposed abundant active sites. • The prepared electrocatalyst presents excellent electrocatalytic performances toward HER, OER and UOR. • Small overpotential is required to drive overall water-splitting under the urea assistance with remarkable stability. • Sustainable energies are investigated to power the electrolyzer for hydrogen generation. [ABSTRACT FROM AUTHOR]