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Developing electrocatalysts with excellent activity and stability for water splitting in acidic media remains a formidable challenge due to the sluggish kinetics and severe dissolution. As a solution, a multi-component doped RuO 2 prepared through a process of dealloying-annealing is presented. The resulting multi-doped RuO 2 possesses a nanoporous structure, ensuring a high utilization efficiency of Ru. Furthermore, the dopants can regulate the electronic structure, causing electron aggregation around unsaturated Ru sites, which mitigates Ru dissolution and significantly enhances the catalytic stability/activity. The representative catalyst (FeCoNiCrTi-RuO 2 ) shows an overpotential of 167 mV at 10 mA cm -2 for oxygen evolution reaction (OER) in 0.5 m H 2 SO 4 solution with a Tafel slope of 53.1 mV dec -1 , which is among the highest performance reported. Moreover, it remains stable for over 200 h at a current density of 10 mA cm -2 . This work presents a promising approach for improving RuO 2 -based electrocatalysts, offering a crucial advancement for electrochemical water splitting., (© 2024 Wiley‐VCH GmbH.)

Developing single-atomic catalysts with superior selectivity and outstanding stability for CO 2 electroreduction is desperately required but still challenging. Herein, confinement strategy and three-dimensional (3D) nanoporous structure design strategy are combined to construct unsaturated single Ni sites (Ni-N 3 ) stabilized by pyridinic N-rich interconnected carbon nanosheets. The confinement agent chitosan and its strong interaction with g-C 3 N 4 nanosheet are effective for dispersing Ni and restraining their agglomeration during pyrolysis, resulting in ultrastable Ni single-atom catalyst. Due to the confinement effect and structure advantage, such designed catalyst exhibits a nearly 100% selectivity and remarkable stability for CO 2 electroreduction to CO, exceeding most reported state-of-the-art catalysts. Specifically, the CO Faradaic efficiency (FE CO ) maintains above 90% over a broad potential range (-0.55 to -0.95 V vs. RHE) and reaches a maximum value of 99.6% at a relatively low potential of -0.67 V. More importantly, the FE CO is kept above 95% within a long-term 100 h electrolyzing. Density functional theory (DFT) calculations explain the high selectivity for CO generation is due to the high energy barrier required for hydrogen evolution on the unsaturated Ni-N 3 . This work provides a new designing strategy for the construction of ultrastable and highly selective single-atom catalysts for efficient CO 2 conversion., (© 2023 Wiley‐VCH GmbH.)

Nitrogen (N) doping of graphene with a three-dimensional (3D) porous structure, high flexibility, and low cost exhibits potential for developing metal-air batteries to power electric/electronic devices. The optimization of N-doping into graphene and the design of interconnected and monolithic graphene-based 3D porous structures are crucial for mass/ion diffusion and the final oxygen reduction reaction (ORR)/battery performance. Aqueous-type and all-solid-state primary Mg-air batteries using N-doped nanoporous graphene as air cathodes are assembled. N-doped nanoporous graphene with 50-150 nm pores and ≈99% porosity is found to exhibit a Pt-comparable ORR performance, along with satisfactory durability in both neutral and alkaline media. Remarkably, the all-solid-state battery exhibits a peak power density of 72.1 mW cm -2 ; this value is higher than that of a battery using Pt/carbon cathodes (54.3 mW cm -2 ) owing to the enhanced catalytic activity induced by N-doping and rapid air breathing in the 3D porous structure. Additionally, the all-solid-state battery demonstrates better performances than the aqueous-type battery owing to slow corrosion of the Mg anode by solid electrolytes. This study sheds light on the design of free-standing and catalytically active 3D nanoporous graphene that enhances the performance of both Mg-air batteries and various carbon-neutral-technologies using neutral electrolytes., (© 2023 Wiley-VCH GmbH.)

Anchoring single metal atom to carbon supports represents an exceptionally effective strategy to maximize the efficiency of catalysts. Recently, dual-atom catalysts (DACs) emerge as an intriguing candidate for atomic catalysts, which perform better than single-atom catalysts (SACs). However, the clarification of the polynary single-atom structures and their beneficial effects remains a daunting challenge. Here, atomically dispersed triple Zn-Co-Fe sites anchored to nitrogen-doped carbon (ZnCoFe-N-C) prepared by one-step pyrolysis of a designed metal-organic framework precursor are reported. The atomically isolated trimetallic configuration in ZnCoFe-N-C is identified by annular dark-field scanning transmission electron microscopy and spectroscopic techniques. Benefiting from the synergistic effect of trimetallic single atoms, nitrogen, and carbon, ZnCoFe-N-C exhibits excellent catalytic performance in bifunctional oxygen reduction/evolution reactions in an alkaline medium, outperforming other SACs and DACs. The ZnCoFe-N-C-based Zn-air battery exhibits a high specific capacity (liquid state: 931.8 Wh kg Zn -1 ), power density (liquid state: 137.8 mW cm -2 ; all-solid-state: 107.9 mW cm -2 ), and good cycling stability. Furthermore, density-functional theory calculations rationalize the excellent performance by demonstrating that the ZnCoFe-N-C catalyst has upshifted d-band center that enhances the adsorption of the reaction intermediates., (© 2023 Wiley-VCH GmbH.)

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., (© 2022 Wiley-VCH GmbH.)

Zn-ion batteries (ZIBs) using aqueous electrolyte, recently, have been a hot topic owing to the high safety, low cost, and high specific energy capacity. However, the formation of dendrite and side reactions on the Zn anode during cycling inhibit the application of ZIBs. An advanced Zn anode by alloying a small amount of Li and Mn with Zn is hereby reported. It is found that Li and Mn can form cationic ions which restrain lateral diffusion of Zn ions and regulate zinc electrodeposition through the electrostatic shield mechanism. As a result, the formation of Zn dendrite is greatly inhibited. This process also mitigates the formation of Zn-based byproduct and Zn passivation. Consequently, the symmetric ZnLiMn/ZnLiMn cell presents a small overpotential of 30 mV at 1 mA cm -2 , greatly enhanced cycling durability (1000 h at a current density of 1 mA cm -2 ), and a dendrite-free morphology after cycles. Moreover, the authors find that the ZnLiMn alloy has greatly enhanced mechanical properties. The assembled ZnLiMn/MnO 2 full cell can retain 96% capacity after 400 cycles at 1 C. Thus, the alloying low-cost Li/Mn strategy is very promising for large-scale production of dendrite-free Zn electrode in rechargeable ZIBs., (© 2022 Wiley-VCH GmbH.)

One major challenge in heterogeneous catalysis is to reduce the usage of noble metals while maintaining the overall catalytic stability and efficiency in various chemical environments. In this work, a series of high-entropy catalysts are synthesized by a chemical dealloying method and find the increased entropy effect and non-noble metal contents would facilitate the formation of complete oxides with low crystallinity. Importantly, an optimal eight-component high-entropy oxide (HEO, Al-Ni-Co-Ru-Mo-Cr-Fe-Ti) is identified, which exhibits further enhanced catalytic activity for the oxygen evolution reaction (OER) as compared to the previously reported quinary AlNiCoRuMo and the widely-used commercial RuO 2 catalysts, and at the same time similar catalytic activity for the oxygen reduction reaction (ORR) as the commercial Pt/C with a half-wave potential of 0.87 V. Such high-performance bi-functional catalysts, however, only require a half loading amount of Ru as compared to the quinary AlNiCoRuMo, due to the underlying Cr-Fe synergistic effects on tuning the electronic structures at active surface sites, as revealed by the first-principles density functional theory calculations of the authors. The eight-component HEO also demonstrates excellent stability under continuous electrochemical working conditions, suitable for a wide range of applications such as metal-air batteries., (© 2022 Wiley-VCH GmbH.)

Single-atom cobalt-based CoNC are promising low-cost electrocatalysts for oxygen reduction reaction (ORR). However, further increasing the single cobalt-based active sites and the ORR activity remain a major challenge. Herein, an acetate (OAc) assisted metal-organic framework (MOF) structure-engineering strategy is developed to synthesize hierarchical accordion-like MOF with higher loading amount and better spatial isolation of Co and much higher yield when compared with widely reported polyhedron MOF. After pyrolysis, the accordion-structured CoNC (CoNC (A)) is loaded with denser CoN 4 active sites (Co: 2.88 wt%), approximately twice that of Co in the CoNC reported. The presence of OAc in MOF also induces the generation of big pores (5-50 nm) for improving the accessibility of active sites and mass transfer during catalytic reactions. Consequently, the CoNC (A) catalyst shows an admirable ORR activity with a E 1/2 of 0.89 V (40 mV better than Pt/C) in alkaline electrolytes, outstanding durability, and absolute tolerance to methanol in both alkaline and acidic media. The CoNC-based Zn-air battery exhibits a high specific capacity (976 mAh g -1 Zn ), power density (158 mW cm -2 ), rate capability, and long-term stability. This work demonstrates a reliable approach to construct single atom doped carbon catalysts with denser accessible active sites through MOF structure engineering., (© 2021 Wiley-VCH GmbH.)

Ir-based binary and ternary alloys are effective catalysts for the electrochemical oxygen evolution reaction (OER) in acidic solutions. Nevertheless, decreasing the Ir content to less than 50 at% while maintaining or even enhancing the overall electrocatalytic activity and durability remains a grand challenge. Herein, by dealloying predesigned Al-based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir. The obtained nanoporous quinary alloys, i.e., nanoporous high-entropy alloys (np-HEAs) provide infinite possibilities for tuning alloy's electronic properties and maximizing catalytic activities owing to the endless element combinations. Particularly, a record-high OER activity is found for a quinary AlNiCoIrMo np-HEA. Forming HEAs also greatly enhances the structural and catalytic durability regardless of the alloy compositions. With the advantages of low Ir loading and high activity, these np-HEA catalysts are very promising and suitable for activity tailoring/maximization., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Developing bifunctional electrocatalysts with high activities and long durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial toward the practical implementation of rechargeable metal-air batteries. Here, a 3D nanoporous graphene (np-graphene) doped with both N and Ni single atoms/clusters is reported. The predoping of N by chemical vapor deposition (CVD) dramatically increases the Ni doping amount and stability. The resulting N and Ni codoped np-graphene has excellent electrocatalytic activities for both the ORR and the OER in alkaline aqueous solutions. The synergetic effects of N and Ni dopants are revealed by density functional theory calculations. The free-standing Ni,N codoped 3D np-graphene shows great potential as an economical catalyst/electrode for metal-air batteries., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)