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The exploitation of low-cost, stable, and highly active electrocatalysts based on earth-abundant metals for hydrogen evolution reaction (HER) is crucial for developing renewable energy techniques. In this work, we report a facile synthesis strategy for in-situ fabrication of 3D hierarchically porous Ni3S2 films on a nanoporous copper substrate (Ni3S2@NPC) by unusual galvanic replacement reaction in the Ethaline-based deep eutectic solvent (DES) under a normal atmosphere. The self-supported nanoporous Ni3S2@NPC electrode is binder-free and exhibits good structural integrity with high conductivity. A mild evolution of bulk gas bubbles (H2-O2 gas mixture) is proved to drive an in-situ structure rearrangement process of the Ni3S2@NPC and results in substantial increases in the HER activity. The activated Ni3S2@NPC (a-Ni3S2@NPC) electrode can serve as a highly efficient and stable electrocatalyst for the HER in water over a wide pH range. Significantly, it displays high-performance HER catalytic activity in acidic media with robust durability over 111 h and functions well under alkaline and neutral conditions. Such a superior catalytic performance of the a-Ni3S2@NPC is mainly due to the unique hierarchically nanoporous architectures and the synergetic effects in it caused by the restructuring NPC skeletons and active components. Our work offers a generic strategy for design and fabrication of many other self-supported transition metal sulfide and phosphide based HER electrocatalysts, and uncovers a new O2-induced electrochemical self-activation mechanism for improving the activity of catalysts.

Self-supported porous Ni–Mo alloy microsphere (Ni–Mo MS) films are fabricated in ethaline via a facile, one-step electrodeposition approach, which can act as highly efficient and durable bifunctional catalysts for both the HER and OER in 1.0 M KOH.

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Wrinkled ultrathin graphitic C3N4 nanosheets (U-g-C3N4) have been successfully synthesized via a thermal condensation process and subsequent rapid cooling treatment in liquid nitrogen. The layer contraction force caused by the rapid cooling process can break the van der Waals forces between the interlayers, thus successfully exfoliating the bulk g-C3N4. The U-g-C3N4 exhibits large specific surface area, effective separation of the photogenerated carriers, and increased visible-light absorbance, which can promote the quantity and lifetime of the photoexcited electrons, resulting in a high photodegradation efficiency of 99.82%. These results show that the interlayer contraction force is a viable option for exfoliating layered materials into a thin-layer structure. This is an interesting and easy method for obtaining thin-layer materials.

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