Nanocage-chain fuel cell catalysts: The expense and scarcity of platinum has driven efforts to improve oxygen-reduction catalysts in proton-exchange membrane fuel cells. Tian et al. synthesized chains of platinum-nickel alloy nanospheres connected by necking regions. These structures can be etched to form nanocages with platinum-rich surfaces that are highly active for oxygen reduction. In fuel cells running on air and hydrogen, these catalysts operated for at least 180 hours. Science , this issue p. 850

In this work, surfactant-free atomically ultrathin Rh nanosheet nanoassemblies (Rh NNs) are synthesized and used for the first time as an effective electrocatalyst in the nitrogen reduction reaction (NRR) at ambient temperature and pressure. The inorganic polymer RhCl₃–K₃Co(CN)₆ cyanogel plays an important role in the generation of ultrathin Rh nanosheets with a clean surface. Due to their unique ultrathin two-dimensional nanosheet structure (ca. 1 nm) with a high specific surface area and modified electronic structure, the surfactant-free Rh NNs demonstrate an excellent catalytic activity for the NRR with a high production yield (NH₃: 23.88 μg h⁻¹ mg_cat ⁻¹) and favorable selectivity (no N₂H₄ generation) at low potential (−0.2 V vs. RHE), outperforming most of the current electrocatalysts reported for the NRR. Except the contribution to the efficient NRR electrocatalysis, this synthesis strategy would provide some new insights into the preparation of ultrathin precious metal nanosheets for energy related applications.

The investigation of highly effective, durable, and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) is a prerequisite for the upcoming hydrogen energy society. To establish a new hydrogen energy system and gradually replace the traditional fossil-based energy, electrochemical water-splitting is considered the most promising, environmentally friendly, and efficient way to produce pure hydrogen. Compared with the commonly used platinum (Pt)-based catalysts, ruthenium (Ru) is expected to be a good alternative because of its similar hydrogen bonding energy, lower water decomposition barrier, and considerably lower price. Analyzing and revealing the HER mechanisms, as well as identifying a rational design of Ru-based HER catalysts with desirable activity and stability is indispensable. In this review, the research progress on HER electrocatalysts and the relevant describing parameters for HER performance are briefly introduced. Moreover, four major strategies to improve the performance of Ru-based electrocatalysts, including electronic effect modulation, support engineering, structure design, and maximum utilization (single atom) are discussed. Finally, the challenges, solutions and prospects are highlighted to prompt the practical applications of Ru-based electrocatalysts for HER.