High-efficiency electrocatalysts with superior activity and stability are crucial to practical applications in water splitting, including the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Downsizing the conventional nanoparticle catalyst to single atoms and constructing single-atom catalysts (SACs) is a rapidly emerging research focus. Because of the involvement of unique single-atom active moieties and the strong metal–support interactions arising from interfacial bonding, SACs as promising alternatives to noble metal-based nanoparticle catalysts exhibit profound power in the HER and OER. Here, we present a perspective on the exciting advances of SACs for HER and OER applications, with an emphasis on innovative synthetic strategies and an in-depth understanding of the structure–activity relationship through a combination of systematic characterization and theoretical studies. Finally, the challenges and some of the critical issues in this field are addressed.

Ir-based nanomaterials are regarded as state-of-the-art cathode electrocatalysts in proton exchange membrane water electrolyzers (PEMWEs). Engineering the morphology of Ir-based three-dimensional architectures as electrocatalysts toward oxygen evolution reaction (OER) has been rarely studied.Here, we report the gelation of Ir x Cu metallic hydrogels self-assembled with ultrafine and nanovoid incorporated building blocks for enhancing the electrocatalytic performance toward OER. The composition-optimized Ir 3 Cu metallic aerogels exhibited improved catalytic activity and durability toward OER. The mesosized voids generated through the in situ galvanic replacement reaction and the macrosized porous systems make a great contribution to the increased number of active sites. First-principle calculations revealed the intrinsic optimized binding energy of Ir by alloying with Cu. The best catalytic performance necessities a balance of the adsorption and desorption energy. The well-defined morphology and enhanced OER electrochemical performances of nanovoid incorporated Ir x Cu metallic aerogels hold great promise in further applications in PEMWEs.

The lithium-sulfur (Li-S) battery is a promising next-generation energy storage technology because of its high theoretical energy and low cost. Extensive research efforts have been made on new materials and...

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The development of efficient Fe−N−C materials enriched with single-atom Fe sites toward the oxygen reduction reaction (ORR) is still a great challenge because Fe atoms are mobile and easily aggregate into nanoparticles during the high-temperature treatment. Herein, we proposed a facile and universal secondary-atom-assisted strategy to prepare atomic iron sites with high density hosted on porous nitrogen-doped carbon nanowires (Fe−NCNWs). The Fe−NCNWs showed an impressive half-wave potential (E 1/2 ) of 0.91 V and average kinetic current density (J K ) of 6.0 mA cm −2 at 0.9 V in alkaline media. They also held a high ORR activity in acidic solution with the E 1/2 of 0.82 V and average J K of 8.0 mA cm −2 at 0.8 V. Density functional theory calculations demonstrated that the high ORR activity achieved is originated from single-atom iron sites that decrease the energy barrier in the reaction path efficiently.