Multi-atom cluster catalysts have turned out to be novel heterogeneous catalysts with atomic dispersion for electrochemical energy applications. Beyond a simple combination of single-atom catalysts, they could offer boosted activity as a result of the synergistic effects between adjacent atoms. Meanwhile, the multiple active sites in the catalytic center may render them versatile binding modes toward adsorbates and provide an opportunity for catalyzing complex reactions with diverse products. Herein, a comprehensive review of the recent development of multi-atom cluster catalysts for electrochemical energy applications is provided. Specifically, the origin of synergistic effects in multi-atom cluster catalysts and related modulation methods are illustrated and summarized. The introduction of multi-atom cluster catalysts to circumvent the scaling relationships as well as their potential for developing new descriptors is then discussed. Subsequently, the methods for fabricating multi-atom cluster catalysts and related characterization techniques are reviewed. This is followed by the discussion of their application in key electrochemical reactions such as water splitting, oxygen reduction, and carbon dioxide/monoxide reduction, as well as the real-time techniques for their mechanistic study. Finally, the future challenges and opportunities concerning the improvement of multi-atom cluster catalysts are outlined, which are essential to make such electrocatalysts viable for electrochemical energy conversion.

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Multi-atom cluster catalysts for efficient electrocatalysis.

A flexible air electrode with excellent activity and outstanding stability is highly desirable for metal-air batteries. Herein, the rational design of CoNi alloys derived intertwined N-doped carbon nanotube arrays onto carbon cloth ([email protected]/CC) is reported, as self-supported air electrodes for flexible zinc-air and aluminum-air batteries. [email protected]/CC exhibits a low potential of 1.56 V at 10 mA cm−2 in OER, along with a half-wave potential of 0.82 V in ORR, which is attributed to abundant active sites including CoNi alloys with optimized adsorption energy, Co/Ni-Nx and N-doped CNTs. The well-designed nanotube array construction with substantial channels on carbon cloth facilitates the mass diffusion and electron delivery, and improves mechanical flexibility. Combining excellent activity and promising flexibility, [email protected]/CC based liquid- and all-solid-state zinc-air batteries exhibit excellent charge/discharge capability and long-term stability. And the liquid- and all-solid-state aluminum-air batteries deliver promising discharge property with a high open circuit voltage as well as commendable flexibility. 

In-situ cobalt-nickel alloy catalyzed nitrogen-doped carbon nanotube arrays as superior freestanding air electrodes for flexible zinc-air and aluminum-air batteries

Science and engineering for non-noble-metal-based electrocatalysts to boost their ORR performance: A critical review

Electrical structures, magnetic polaron and lithium ion dynamics in three transition metal doped LiFe1 − xMxPO4 (M = Mn, Co and La) cathode material for Li ion batteries from density functional theory study

The electrochemical CO2 reduction reaction (CO2RR) to yield high-value added fuels and chemicals provides a promising approach towards global carbon neutrality. Constant endeavors have been devoted to the exploration of high-efficiency catalyst with rapid reaction kinetics, low energy input, and high selectivity. In addition to the maximum metal atomic utilization and unique catalytic performance of single-atom catalyst (SAC), dual-atomic-site catalysts (DASCs) offer more sophisticated and tunable atomic structure through the modulations of another adjacent metal atom, which can bring new opportunities for CO2RR as a deeper extension of SACs and have recently aroused surging interest. In this review, we highlight the recent advances on DASCs for enhancing CO2RR. First, the classification, synthesis, and identification of DASCs are provided according to the geometric structure and electronic configuration of dual-atomic active sites. Then, the catalytic applications of DASCs in CO2RR are categorized based on marriage-type, hetero-nuclear, and homo-nuclear dual-atomic sites. Particularly, the structure-activity relationship of DASCs in CO2RR is elaborately summarized through systematically analyzing the reaction pathways and the atom structures. Finally, the opportunities and challenges are proposed for inspiring the design of future DASCs with high structural accuracy and high CO2RR activity and selectivity. 

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Emerging dual-atomic-site catalysts for electrocatalytic CO2 reduction

Developing highly active, selective, and stable electrocatalysts for the carbon dioxide reduction reaction (CO2RR) is crucial to establish a CO2 conversion system for industrial implementation and, therefore, to realize an artificially closed carbon loop. This can only be achieved through the rational material design based upon the knowledge of the operational active site at the molecular scale. Enlightened by theoretical screening, herein, we for the first time manipulate a novel Ni-Cu atomic pair configuration toward improved CO2RR performance. Systematic characterizations and theoretical modeling reveal that the secondary Cu metal incorporation positively shifts the Ni 3d orbital energy to the Fermi level and thus accelerates the rate-determining step, *COOH formation. In addition, the intrinsic inactivity of Cu toward the competing hydrogen evolution reaction causes a considerable reaction barrier for water dissociation on the Ni-Cu moiety. Due to these attributes, the as-developed Ni/Cu-N-C catalyst exhibits excellent catalytic activity and selectivity, with a record-high turnover frequency of 20,695 h-1 at -0.6 V (vs RHE) and a maximum Faradaic efficiency of 97.7% for CO production. Furthermore, the dynamic structure evolution monitored by operando X-ray absorption fine-structure spectroscopy unveils the interaction between the Ni center and CO2 molecules and the synergistic effect of the Ni-Cu atomic pair on CO2RR activity.

Quasi-Covalently Coupled Ni-Cu Atomic Pair for Synergistic Electroreduction of CO2.

Dual–single‐atom catalysts with synergistic effect of adjacent atomic metal sites show a great potential for oxygen reduction reaction (ORR). Herein, a dynamical synthetic strategy is demonstrated for the rational design of dual‐atom catalyst ((Zn, Cu)−NC) with non‐covalent Cu and Zn sites as nitrogen‐doped carbon as support. Owing to the non‐covalent interaction of Zn and Cu atomic pair sites, (Zn, Cu)−NC exhibits significant performances for ORR, surpassing the catalysts with individual Zn or Cu site. The theoretical calculations reveal that (Zn, Cu)−NC can highly activate the linear O2 molecule via the non‐covalent interaction between Zn and Cu pairs, providing the more effective overlap between the metal 3d orbitals and O 2p orbital. Therefore, the ORR activity is optimized with the improvement of the adsorption configuration and adsorption energy of O2. Further, both liquid and quasi‐solid zinc−air batteries with (Zn, Cu)−NC as air cathodes achieve remarkable energy density and stability. This research proposes a facile synthetic strategy to construct single‐atom catalysts and presents an insightful understanding of the non‐covalent interplay between heteronuclear metal atoms in dual‐atom catalysts.

Non‐Covalent Interaction of Atomically Dispersed Cu and Zn Pair Sites for Efficient Oxygen Reduction Reaction

Surface reconstruction of Ni‐rich layered oxides (NLO) degrades the cycling stability and safety of high‐energy‐density lithium‐ion batteries (LIBs), which challenges typical surface‐modification approaches to build a robust interface with electrochemical activity. Here, a strategy of leveraging the low‐strain analogues of Li‐ and Mn‐rich layered oxides (LMR) to reconstruct a stable surface on the Ni‐rich layered cathodes is proposed. The new surface structure not only consists of a gradient chemical composition but also contains a defect‐rich structure regarding the formation of oxygen vacancies and cationic ordering, which can simultaneously facilitate lithium diffusion and stabilize the crystal structure during the (de)lithiation. These features in the NLO lead to a dramatic improvement in electrochemical properties, especially the cyclability under high voltage cycling, exhibiting the 30% increase in capacity retention after 200 cycles at the current density of 1 C (3.0–4.6 V). The findings offer a facile and effective way to regulate defect chemistry and surface structure in parallel on Ni‐rich layered structure cathodes to achieve high‐energy density LIBs.

Regulation of Surface Defect Chemistry toward Stable Ni‐Rich Cathodes

Single atom tailored metal nanoparticles represent a new type of catalysts. Herein, we demonstrate a single atom-cavity coupling strategy to regulate performance of single atom tailored nano-catalysts. Selective atomic layer deposition (ALD) was conducted to deposit Ru single atoms on the surface concavities of PtNi nanoparticles (Ru-ca-PtNi). Ru-ca-PtNi exhibits a record-high activity for methanol oxidation reaction (MOR) with 2.01 A mg -1 Pt . Also, Ru-ca-PtNi showcases a significant durability with only 16% activity loss. Operando electrochemical Fourier transform infrared spectroscopy (FTIR) and theoretical calculations demonstrate Ru single atoms coupled to cavities accelerate the CO removal by regulating d -band centre position. Further, the high diffusion barrier of Ru single atoms in concavities accounts for excellent stability. The developed Ru-ca-PtNi via single atom-cavity coupling opens an encouraging pathway to design highly efficient single atom-based (electro)catalysts.

Dong-dong Su

Papers

Quasi-Covalently Coupled Ni-Cu Atomic Pair for Synergistic Electroreduction of CO2.

Non‐Covalent Interaction of Atomically Dispersed Cu and Zn Pair Sites for Efficient Oxygen Reduction Reaction

Regulation of Surface Defect Chemistry toward Stable Ni‐Rich Cathodes

Selectively Coupling Ru Single Atoms to PtNi Concavities for High Performance Methanol Oxidation via d-Band Center Regulation.

Regulated electronic structure and improved electrocatalytic performances of S-doped FeWO4 for rechargeable zinc-air batteries