Asymmetric diatomic catalysts (ADCs) represent a promising class of sustainable electrocatalysts, featuring exceptional atom efficiency and dual active sites with asymmetric coordination environments. The asymmetric charge distribution in ADCs generates a local built-in electric field, enhancing charge separation/transfer and facilitating synergistic multi-step catalysis. This inherent structural complexity boosts catalytic performance by modulating the adsorption orientation and electronic configuration of intermediates. Importantly, the establishment of precise structure-activity correlations and the elucidation of underlying reaction mechanisms are of critical significance. This review provides a comprehensive overview of recent advancements in ADCs, with particular emphasis on classification methodologies, the application of artificial intelligence (AI), advanced characterization techniques, and their applications in key electrocatalytic reactions, such as oxygen reduction (ORR), oxygen evolution (OER), hydrogen evolution (HER), and carbon dioxide reduction (CO₂RR). Finally, the unresolved challenges and proposes potential research directions to advance the implementation of ADCs in energy systems are discussed.

Electrochemical CO₂ reduction reaction (CO₂RR) into high-value chemicals and fuels is recognized as a promising strategy for mitigating energy and environmental challenges. However, this process frequently faces limitations due to inadequate selectivity towards specific products and insufficient electrochemical stability. Main group indium (In) catalysts have emerged as promising materials for CO₂RR to highly valued formate. In this study, we constructed an indium cluster material with charge-asymmetric atomic structure anchored on nitrogen-free carbon nanoframeworks (designated as In Clu/C), which exhibits exceptional efficiency as a CO₂RR catalyst for formate production. Notably, the In Clu/C achieves a remarkable formate Faradaic efficiency of 98.7% at −0.70 V. Furthermore, in-situ X-ray absorption spectroscopy (XAS) measurements reveal that the superior catalytic performance can be attributed to partially positively charged In^δ+ (0 < δ < 3) active sites. This discovery may provide new insights into the precise synthesis of metal cluster catalysts for environmental and energy applications.

By incorporating a limited number of precious metal atoms into the base metal, the single-atom alloy catalyst not only optimizes the electronic structure and stability of the catalyst but also emerges as an innovative material that enhances the efficiency and selectivity of catalytic reactions. RuCo single-atom alloy electrocatalyst supported on S, N co-doped carbon nanosheets (RuCo SAA/SNC) uniformly distributed on nitrogen, sulfur co-doped carbon nanosheets was prepared by two-step pyrolysis and carbonization. The incorporation of Ru not only optimizes the atomic utilization of Ru but also enhances the charge conduction properties of the surface Co species, thereby increasing the evolution and migration rates of hydrogen ions. In a 0.5 M H₂SO₄ solution, the RuCo SAA/SNC catalyst demonstrates a tafel slope of 27.5 mV·dec⁻¹ and an overpotential of merely 43 mV at 10 mA·cm⁻². This work achieves enhanced catalytic performance and stability by precisely regulating the atomic-level structure of single-atom alloy catalysts, thereby promoting their widespread application in energy conversion and green chemistry.

Single atom catalysts (SACs) play a crucial role in energy catalysis due to their distinct coordination environment and high atomic utilization efficiency. This study focuses on the synthesis of a monatomic Cu catalyst with Cu–N₁C₁ coordination anchored to N-doped Ti₃C₂T_x MXene (Cu SA@N-Ti₃C₂T_x) to achieve efficient reduction of CO₂ to CO. Detailed characterization, including morphology and multispectral analysis, confirmed the uniform distribution of asymmetrically coordinated Cu atoms in unsaturated C–Cu–N bridge fragments on Ti₃C₂T_x. The Cu SA@N-Ti₃C₂T_x catalyst exhibited an excellent CO selectivity with Faraday efficiency of 97.4% at −0.58 V vs. reversible hydrogen electrode (RHE) and satisfactory durability. The in situ X-ray absorption fine structure (XAFS) results confirmed that the carbon dioxide reduction reaction (CO₂RR) product distribution is mainly affected by potential-dependent valence change of Cu species. These findings highlight the extensive potential of tuning coordination structure of MXene-based single-atom catalysts for CO₂ reduction reactions.

Carbon-based dual-metal sites catalysts (DMSCs) have emerged as a new frontier in the field of sustainable energy due to their unique coordination environments, electronic structure, and the maximized atom utilization. The reasonable utilization of carbon-based DMSCs provides new possibilities to achieve the outstanding catalytic performance, remarkable selectivity, and recyclability in energy-related catalysis. Based on this, this review intends to summarize the recent breakthroughs in carbon-based DMSCs for the energy catalysis. Firstly, the definition and classifications of DMSCs are proposed, mainly dividing into three types (isolated dual-metal site pairs, binuclear homologous dual-metal sites pairs, and binuclear heterologous dual-metal sites pairs). Subsequently, we discuss the potential of DMSCs targeting on energy conversion reactions, such as electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO₂ reduction reaction (CO₂RR), and N₂ reduction reaction (NRR). Finally, we predict the remaining challenges and possible opportunities on the unique carbon-based DMSCs for energy applications in the future.

Developing cost-effective and high-efficiency oxygen reduction reaction (ORR) catalysts is imperative for promoting the substantial progress of fuel cells and metal-air batteries. The coordination and geometric engineering of single-atom catalysts (SACs) occurred the promising approach to overcome the thermodynamics and kinetics problems in high-efficiency electrocatalysis. Herein, we rationally constructed atomically dispersed Co atoms on porous N-enriched graphene material C₂N (CoSA-C₂N) for efficient oxygen reduction reaction (ORR). Systematic characterizations demonstrated the active sites for CoSA-C₂N is as identified as coordinatively unsaturated Co-N₂ moiety, which exhibits ORR intrinsic activity. Structurally, the porous N-enriched graphene framework in C₂N could effectively increase the accessibility to the active sites and promote mass transfer rate, contributing to improved ORR kinetics. Consequently, CoSA-C₂N exhibited superior ORR performance in both acidic and alkaline conditions as well as impressive long-term durability. The coordination and geometric engineering of SACs will provide a novel approach to advanced catalysts for energy related applications.

Transition metal sulfides with homogeneous multi-metallic elements promise high catalytic performance for water electrolysis owing to the unique structure and highly tailorable electrochemical property. Most existing synthetic routes require high temperature to ensure the uniform mixing of various elements, making the synthesis highly challenging. Here, for the first-time novel carbon fiber supported high-entropy Co-Zn-Cd-Cu-Mn sulfide (CoZnCdCuMnS@CF) nanoarrays are fabricated by the mild cation exchange strategy. Benefiting from the synergistic effect among multiple metals and the strong interfacial bonding between high-entropy Co-Zn-Cd-Cu-Mn sulfide nanoarrays and the carbon fiber support, CoZnCdCuMnS@CF exhibits superior catalytic activity and stability toward overall water splitting in alkaline medium. Impressively, CoZnCdCuMnS@CF only needs low overpotentials of 173 and 220 mV to reach the current density of 10 mA•cm⁻², with excellent durability for over 70 and 113 h for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) respectively. More importantly, the bifunctional electrode (CoZnCdCuMnS@CF||CoZnCdCuMnS@CF) for overall water splitting can deliver a small cell voltage of 1.63 V to afford 10 mA•cm⁻² and exhibit outstanding stability of negligible decay after 73 h continuous operation. This work provides a viable synthesis route toward advanced high-entropy materials with great potential applications.

Rational design and construction of low-cost and highly efficient electrocatalysts for hydrogen evolution reaction (HER) is meaningful but challenging. Herein, a robust three dimensional (3D) hollow CoSe₂@ultrathin MoSe₂ core@shell heterostructure (CoSe₂@MoSe₂) is proposed as an efficient HER electrocatalyst through interfacial engineering. Benefitting from the abundant heterogeneous interfaces on CoSe₂@MoSe₂, the exposed edge active sites are maximized and the charge transfer at the hetero-interfaces is accelerated, thus facilitating the HER kinetics. It exhibits remarkable performance in pH-universal conditions. Notably, it only needs an overpotential (η₁₀) of 108 mV to reach a current density of 10 mA·cm⁻² in 1.0 M KOH, outperforming most of the reported transition metal selenides electrocatalysts. Density functional theory (DFT) calculations unveil that the heterointerfaces synergistically optimize the Gibbs free energies of H₂O and H* during alkaline HER, accelerating the reaction kinetics. The present work may provide new construction guidance for rational design of high-efficient electrocatalysts.