High-entropy alloys have received considerable attention in the field of catalysis due to their exceptional properties. However, few studies hitherto focus on the origin of their outstanding performance and the accurate identification of active centers. Herein, we report a conceptual and experimental approach to overcome the limitations of single-element catalysts by designing a FeCoNiXRu (X: Cu, Cr, and Mn) High-entropy alloys system with various active sites that have different adsorption capacities for multiple intermediates. The electronegativity differences between mixed elements in HEA induce significant charge redistribution and create highly active Co and Ru sites with optimized energy barriers for simultaneously stabilizing OH* and H* intermediates, which greatly enhances the efficiency of water dissociation in alkaline conditions. This work provides an in-depth understanding of the interactions between specific active sites and intermediates, which opens up a fascinating direction for breaking scaling relation issues for multistep reactions.

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To understand the mechanism of the reaction catalyzed by high-entropy-alloy (HEA) electrocatalysts, it has become increasingly crucial to investigate the chemical nature of the adsorbed intermediate species on the metal...

overcome the thermodynamic and kinetic stability of CO 2 molecules. [9][10][11] Various products, including CO, formic acid, and C 2+ products, have been achieved. [12][13][14] However, their catalytic efficiency and product selectivity for practical application are still limited by the large overpotential and undesirable competition of the hydrogen evolution reaction (HER). [15][16][17][18] Therefore, it is urgent to accurately control electrocatalysts at the atomic scale to break the inherent scaling relationship for the CO 2 RR.Recently, transition metal single-atom catalysts (SACs) have attracted tremendous attention for the CO 2 RR due to their sufficient atom utilization efficiency and desirable electronic states. [19][20][21] Ni single atom (SA) supported on graphene demonstrates good performance for CO 2 reduction to CO; however, it also suffers from a high onset potential due to the weak binding strengths of the intermediates at the Ni-N-C sites, leading to a high energy barrier to form *COOH intermediates. [22,23] Fe SA exhibits a low onset potential for the CO 2 RR, but unfortunately, the strong binding of *CO at the Fe sites seriously lowers the Faraday efficiency (FE) and stability. [24][25][26][27] Therefore, balancing the adsorption strength for both *COOH and *CO intermediates on only one kind of single metal site is a great challenge. It has been reported that dual-single-atom (DSA) catalysts with substantially different coordination environments and quantum size effects have the potential to surpass the well-established SACs for the CO 2 RR. [28][29][30][31][32] However, insufficient theory-designed DSA catalysts impede the development of DSA catalysts with specific catalytic activity. [31] Furthermore, the understanding regarding the mechanism for the enhanced catalytic process lacks in-depth research both experimentally and theoretically. [32] Most of the reported DACs have primarily focused on the thermodynamic pathway, for example, the Gibbs free energy, while the electron interactions between dual atoms and the kinetic pathway are equally indispensable for obtaining a thorough comprehension of this enhanced CO 2 RR process. [33][34][35][36][37] Therefore, the rational design of high-performance DSA remains conceptually challenging, and the electronic variation of each metal site during the CO 2 RR process has yet to be explored.Herein, we design a DSA catalyst consisting of atomically dispersed Cu and Ni bimetal sites, and the electronegativity offset between the Cu and neighboring Ni atoms significantly Achieving efficient efficiency and selectivity for the electroreduction of CO 2 to value-added feedstocks has been challenging, due to the thermodynamic stability of CO 2 molecules and the competing hydrogen evolution reaction. Herein, a dual-single-atom catalyst consisting of atomically dispersed CuN 4 and NiN 4 bimetal sites is synthesized with electrospun carbon nanofibers (CuNi-DSA/CNFs). Theoretical and experimental studies reveal the strong electron interactions induced by the electro...

Strain engineering in bimetallic alloy structures is of great interest in electrochemical CO2 reduction reactions (CO2RR), in which it simultaneously improves electrocatalytic activity and product selectivity by optimizing the binding properties of intermediates. However, a reliable synthetic strategy and systematic understanding of the strain effects in the CO2RR are still lacking. Herein, we report a strain relaxation strategy used to determine lattice strains in bimetal MNi alloys (M = Pd, Ag, and Au) and realize an outstanding CO2-to-CO Faradaic efficiency of 96.6% and show the outstanding activity and durability toward a Zn-CO2 battery. Molecular dynamics (MD) simulations predict that the relaxation of strained PdNi alloys (s-PdNi) is correlated with increases in synthesis temperature, and the high temperature activation energy drives complete atomic mixing of multiple metal atoms to allow for regulation of lattice strains. Density functional theory (DFT) calculations reveal that strain relaxation effectively improves CO2RR activity and selectivity by optimizing the formation energies of *COOH and *CO intermediates on s-PdNi alloy surfaces, as also verified by in situ spectroscopic investigations. This approach provides a promising approach for catalyst design, enabling independent optimization of formation energies of reaction intermediates to improve catalytic activity and selectivity simultaneously.

Developing highly efficient electrocatalysts while revealing the active site and reaction mechanism is essential for electrocatalytic water splitting. To overcome the number and location limitations of defects in the electrocatalyst induced by conventional transition-metal atom (e.g. Fe, Co, and Ni) surface doping, we report a facile strategy of substitution with lower electronegative vanadium in the cobalt carbide, leading to larger amounts of defects in the whole lattice. The self-supported and quantitatively substituted V x Co3–x C (0 ≤ x ≤ 0.80) was one-step synthesized in the electrospun carbon nanofibers (CNFs) through the solid-state reaction. Particularly, the V0.28Co2.72C/CNFs exhibit superior hydrogen evolution reaction and oxygen evolution reaction activity and deliver a current density of 10 mA cm–2 at 1.47 V as the alkaline electrolyzer, which is lower than the values for the Pt/C–Ir/C couple (1.60 V). The operando Raman spectra and density functional theory calculations show that the enhanced electron transfer from V to the orbit of the Co atom makes Co a local negative charge center and leads to a significant increase in efficiency for overall water splitting.

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