carrier with an extremely high energy density (approximately 142 MJ kg −1 ) and zero-carbon content, has been regarded as a promising clean fuel. [1,2] In this context, electrochemical water splitting, which converts electricity into storable hydrogen, is a viable and efficient solution to mitigate severe energy shortages and greenhouse gas emissions. [3] Among these strategies, hydrogen and oxygen evolution reactions, which occur on the cathode and anode, respectively, in a water electrolyzer, are considered as two critical half-reactions of the water-splitting process. [4] Theoretically, water splitting requires a thermodynamic Gibbs free energy (ΔG) of approximately 237.2 kJ mol −1 , corresponding to a standard potential (ΔE) of 1.23 V versus a reversible hydrogen electrode (RHE), which allows the thermodynamically uphill reaction to occur in the electrolyzer. [5] However, the unfavorable thermodynamics and resulting large overpotential are the main barriers to the scalable implementation of water electrolysis for hydrogen generation. [6,7] Currently, noble metal-based electrocatalysts exhibit the most efficient activity for water splitting, particularly Pt-based hydrogen evolution reaction (HER) catalysts and Ir/Ru-based oxygen evolution reaction (OER) catalysts. [8,9] Nevertheless, the scarcity and high price of precious metals severely impede their widespread use in commercial water-splitting applications. Taking these limitations into Electrochemical water splitting has attracted significant attention as a key pathway for the development of renewable energy systems. Fabricating efficient electrocatalysts for these processes is intensely desired to reduce their overpotentials and facilitate practical applications. Recently, metal-organic framework (MOF) nanoarchitectures featuring ultrahigh surface areas, tunable nanostructures, and excellent porosities have emerged as promising materials for the development of highly active catalysts for electrochemical water splitting. Herein, the most pivotal advances in recent research on engineering MOF nanoarchitectures for efficient electrochemical water splitting are presented. First, the design of catalytic centers for MOF-based/derived electrocatalysts is summarized and compared from the aspects of chemical composition optimization and structural functionalization at the atomic and molecular levels. Subsequently, the fast-growing breakthroughs in catalytic activities, identification of highly active sites, and fundamental mechanisms are thoroughly discussed. Finally, a comprehensive commentary on the current primary challenges and future perspectives in water splitting and its commercialization for hydrogen production is provided. Hereby, new insights into the synthetic principles and electrocatalysis for designing MOF nanoarchitectures for the practical utilization of water splitting are offered, thus further promoting their future prosperity for a wide range of applications.

Developing low-cost electrocatalysts for efficient and robust oxygen evolution reaction (OER) is the key for scalable water electrolysis, for instance, NiFebased materials. Decorating NiFe catalysts with other transition metals offers a new path to boost their catalytic activities but often suffers from the low controllability of the electronic structures of the NiFe catalytic centers. Here, we report an interfacial atomsubstitution strategy to synthesize an electrocatalytic oxygen-evolving NiFeV nanofiber to boost the activity of NiFe centers. The electronic structure analyses suggest that the NiFeV nanofiber exhibits abundant high-valence Fe via a charge transfer from Fe to V. The NiFeV nanofiber supported on a carbon cloth shows a low overpotential of 181 mV at 10 mA cm À 2 , along with long-term stability (> 20 h) at 100 mA cm À 2 . The reported substitutional growth strategy offers an effective and new pathway for the design of efficient and durable non-noble metal-based OER catalysts.

Developing low‐cost electrocatalysts for efficient and robust oxygen evolution reaction (OER) is the key for scalable water electrolysis, for instance, NiFe‐based materials. Decorating NiFe catalysts with other transition metals offers a new path to boost their catalytic activities but often suffers from the low controllability of the electronic structures of the NiFe catalytic centers. Here, we report an interfacial atom‐substitution strategy to synthesize an electrocatalytic oxygen‐evolving NiFeV nanofiber to boost the activity of NiFe centers. The electronic structure analyses suggest that the NiFeV nanofiber exhibits abundant high‐valence Fe via a charge transfer from Fe to V. The NiFeV nanofiber supported on a carbon cloth shows a low overpotential of 181 mV at 10 mA cm−2, along with long‐term stability (>20 h) at 100 mA cm−2. The reported substitutional growth strategy offers an effective and new pathway for the design of efficient and durable non‐noble metal‐based OER catalysts.