Electrochemical water splitting is a promising technology for sustainable conversion, storage, and transport of hydrogen energy. Searching for earth‐abundant hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts with high activity and durability to replace noble‐metal‐based catalysts plays paramount importance in the scalable application of water electrolysis. A freestanding electrode architecture is highly attractive as compared to the conventional coated powdery form because of enhanced kinetics and stability. Herein, recent progress in developing transition‐metal‐based HER/OER electrocatalytic materials is reviewed with selected examples of chalcogenides, phosphides, carbides, nitrides, alloys, phosphates, oxides, hydroxides, and oxyhydroxides. Focusing on self‐supported electrodes, the latest advances in their structural design, controllable synthesis, mechanistic understanding, and strategies for performance enhancement are presented. Remaining challenges and future perspectives for the further development of self‐supported electrocatalysts are also discussed.

The electrocatalytic nitrogen reduction reaction (NRR) is an alternative eco‐friendly strategy for sustainable N2 fixation with renewable energy. However, NRR suffers from sluggish kinetics owing to difficult N2 adsorption and N≡N cleavage. Now, nanoporous palladium hydride is reported as electrocatalyst for electrochemical N2 reduction under ambient conditions, achieving a high ammonia yield rate of 20.4 μg h−1 mg−1 with a Faradaic efficiency of 43.6 % at low overpotential of 150 mV. Isotopic hydrogen labeling studies suggest the involvement of lattice hydrogen atoms in the hydride as active hydrogen source. In situ Raman analysis and density functional theory (DFT) calculations further reveal the reduction of energy barrier for the rate‐limiting *N2H formation step. The unique protonation mode of palladium hydride would provide a new insight on designing efficient and robust electrocatalysts for nitrogen fixation.

Nanoporous Ni–Fe–P prepared by dealloying exhibits excellent bifunctional catalytic activity for HER and OER under alkaline conditions.

We present the rational synthesis of nanoporous CuS for the first time by chemical dealloying method. The morphologies of the CuS catalysts are controlled by the composition of the original amorphous alloys. Nanoporous Cu2S is firstly formed during the chemical dealloying process, and then the Cu2S transforms into CuS. The nanoporous CuS exhibits excellent photocatalytic activity for the degradation of the methylene blue (MB), methyl orange (MO) and rhodamine B (RhB). The excellent photocatalytic activity of the nanoporous CuS is mainly attributed to the large specific surface area, high adsorbing capacity of dyes and low recombination of the photo generated electrons and holes. In the photo degradation process, both chemical and photo generated hydroxyl radicals are generated. The hydroxyl radicals are favor in the oxidation of the dye molecules. The present modified dealloying method may be extended for the preparation of other porous metal sulfide nanostructures.

Seawater electrolysis under alkaline conditions presents an attractive alternative to traditional freshwater electrolysis for mass sustainable high-purity hydrogen production. However, the lack of active and robust electrocatalysts severely impedes the industrial application of this technology. Herein, carbon-doped nanoporous cobalt phosphide (C-Co 2 P) prepared by electrochemical dealloying is reported as an electrocatalyst for hydrogen evolution reaction (HER). The C-Co 2 P achieves an overpotential of 30 mV at a current density of 10 mA cm −2 in 1 m KOH, along with impressive catalytic activity and stability at large current densities in artificial alkaline seawater electrolyte containing mixed chlorides of NaCl, MgCl 2 , and CaCl 2 . Experimental analysis and density functional theory calculations reveal that the C atom with strong electronegativity and small atomic radius can tailor the electronic structure of Co 2 P, leading to weakened Co-H bonding toward promoted HER kinetics. Moreover, the C doping introduces a two-stepped H delivery pathway by forming C-H ad intermediate, thus reducing the energy barrier of water dissociation. This study offers a new vision toward the development of seawater electrolysis for large-scale hydrogen production.

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