Heteronuclear double-atom catalysts, unlike single atom catalysts, may change the charge density of active metal sites by introducing another metal single atom, thereby modifying the adsorption energies of reaction intermediates and increasing the catalytic activities. First, density functional theory calculations are used to figure out the best combination by modeling two transition-metal atoms from Fe, Co, and Ni onto N-doped graphene. Generally, Fe and Co sites are highly active for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), respectively. The combination of Co and Fe to form CoFe–N–C not only further improves the Fe’s ORR and Co’s OER activities but also greatly enhances the Co site’s ORR and Fe site’s OER activities. Then, we synthesize the CoFe–N–C by a two-step pyrolysis process and find that the CoFe–N–C exhibits exceptional ORR and OER electrocatalytic activities in alkaline media, significantly superior to Fe–N–C and Co–N–C and even commercial catalysts.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202202071. The development of low-Pt catalysts with high activity and durability is critical for fuel cells. Here, Pt-skin wrapped sub-5 nm PtCo intermetallic nanoparticles are successfully mounted on single atom Co-N-C support by exploiting the barrier effect of Co-anchor. According to a collaborative experimental and computational investigation, the increased oxygen reduction reaction activity of PtCo/Co-N-C arises from the direct electron transfer from PtCo to Co-N-C, and the resulting optimal d-band center of Pt. Owing to such unique electronic structure interaction and synergistic effect, the specific and mass activities of PtCo/Co-N-C are up to 4.20 mA cm −2 and 2.71 A mg Pt −1 , respectively, with barely degraded stability after 40 000 CV cycles. The PtCo/ Co-N-C also exhibits outstanding activity as an ethanol electrocatalyst. This work shows a new and effective route to boost the overall efficiency of direct ethanol fuel cells in acidic media by integrating intermetallic low-Pt alloys and single atom carbon support.

Nanostructured high-entropy materials such as alloys, oxides, etc., are attracting extensive attention because of their widely tunable surface electronic structure/catalytic activity through mixing different elements in one system. To further...

We report theoretical evidence of a liquid-liquid phase transition (LLPT) in liquid silicon carbide under nanoslit confinement. The LLPT is characterized by layering transitions induced by confinement and pressure, accompanying the rapid change in density. During the layering transition, the proportional distribution of tetracoordinated and pentacoordinated structures exhibits remarkable change. The tricoordinated structures lead to the microphase separation between silicon (with the dominant tricoordinated, tetracoordinated, and pentacoordinated structures) and carbon (with the dominant tricoordinated structures) in the layer close to the walls. A strong layer separation between silicon atoms and carbon atoms is induced by strong wall-liquid forces. Importantly, the pressure confinement phase diagram with negative slopes for LLPT lines indicates that, under high pressure, the LLPT is mainly confinement-induced, but under low pressure, it becomes dominantly pressure-induced.

Although multicomponent transition-metal oxides have been widely studied as electrocatalysts in both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), precise control of catalytic activities by varying the composition of these metal elements is not an easy task. In this work, we introduce a generic and scalable synthetic method by dealloying a series of Al-rich precursor alloys to produce Mn 3 O 4 -based and FeCo-based spinel oxide nanocomposites. It is found that these Mn 3 O 4 -based oxides are highly active for the ORR; doping Mn 3 O 4 with Co further enhances the activity while doping with Fe decreases it. For the OER, doping the FeCo-based oxides with Cr, V, or Ni significantly enhances the activity among which Cr is the most effective dopant. Moreover, the addition of Ni into the precursor alloy would inhibit the doping of the negative Fe element into the obtained Mn 3 O 4 after dealloying an AlFeCoNiMn precursor. The obtained (FeCoNi) 3 O 4 /Mn 3 O 4 nanocomposite exhibits a high bifunctional electrocatalytic performance, which is comparable with that of the commercial Pt/C + IrO 2 combination. When incorporated into a Zn−air battery, the battery can be stably discharged/charged over 400 h with an open-circuit voltage of 1.44 V and a narrow voltage gap of ∼0.7 V at 2.0 mA cm −2 .

Modifying the geometric and electronic structures of metal−N−C single-atom catalysts to improve their catalytic activities is quite desirable and challenging. Here, theoretical analysis and experiment indicate the inherent synergistic effect of dual metal sites in Ndoped carbon for bifunctional ORR and OER. Specifically, introducing Ru to generate RuFe−N−C or RuCo−N−C double-atom catalysts (DACs) can significantly enhance the bifunctional ORR/OER activities of Fe(Co) and Ru sites, exceeding the equivalent single metal Fe(Co)− N−C and Ru−N−C. Investigations of a series of RuM−N−C DACs reveal that the intriguing synergistic effect results from the modified charge density and d-band center by combining two optimized metal atoms, which affects adsorption energies of intermediates and catalytic activity. Based on these theoretical guidelines, RuFe−N−C is synthesized using a bimetal MOF as the precursor, and it exhibits exceptional ORR/ OER activities in alkaline media with a small ΔE of 0.63 V, significantly outperforming Fe−N−C, Ru−N−C, and even commercial Pt/C-RuO 2 .

Molecular dynamics simulation has been carried out to explore the configuration and quantity threshold of multiple graphene nanoribbons (GNRs) in single-walled carbon nanotube (SWCNT). The simulation results showed that several GNRs tangled together to form a perfect spiral structure to maximize the π-π stacking area when filling inside SWCNT. The formation of multiple helical configuration is influenced by the combined effect of structure stability, initial arrangement and tube space, meanwhile its forming time is related to helical angle. The simulated threshold of GNRs in SWCNT decreases with GNR width but increases with SWCNT diameter, and two formulas have come up in this study to estimate the quantity threshold for GNRs. It has been found that multilayered graphite is hard to be stripped in SWCNT because the special helical configuration with incompletely separated GNRs is metastable. This work provides a possibility to control the configuration of GNR@SWCNT.

Understanding the fundamental relationship between the structural information of electrocatalysts and their catalytic activities plays a key role in controlling many important electrochemical processes. Recently, single-atom catalysts (SACs) with so-called...