As affordable electrocatalysts for oxygen reduction reactions (ORR) in metal-air batteries, nitrogen-carbon supported atomically dispersed single-atom transition-metal electrocatalysts are emerging. Accurately modulating the first-shell coordination of single-atom metal sites remains challenging, which impedes the elucidation of geometric/electronic structures for optimizing ORR catalysts. Aiming to tackle this challenge by rational design and constructing an asymmetric coordination model catalyst Co-B/N-C, herein we unravel that asymmetric B-coordination stimulates the generation of Co high spin state (t_2g5e_g2). By using X-ray absorption spectroscopy (XAS), we confirm Co active sites are atomically dispersed with a first-shell coordination of boron and nitrogen atom (Co-B₁N₃). Thus, the adsorption strength and electron transfer between the cobalt centers and the reactants/intermediates were boosted for optimal ORR capacity (E_1/2 = 0.87 V). Our work will provide valuable new perspectives on the strategic development of high-performance magnetic metal catalysts for ORR.

Ti₃C₂ MXene is an auspicious energy storage material due to its metallic conductivity and layered assembly. However, in the real working condition of electrochemical energy storage with long cycle charging–discharging, a structural collapse is usually caused by the stacking of its layers creating a large attenuation of specific capacitance. Inspired by the superlattice effect of magic angle graphene, we conducted microscopical regulation of rotation mismatch on the Ti₃C₂ lattice; consequently, a hexagonal few-layered Ti₃C₂ free-standing film constructed with Moiré-superlattices. Such finding not only solves the problem of Ti₃C₂ structural collapse but also dramatically improves the specific capacitance of Ti₃C₂ as a supercapacitor electrode under long cycle charging and discharging. The ultra-stable energy storage of this electrode material in a neutral aqueous electrolyte was realized. Moreover, the formation mechanism of rotating Moiré pattern is revealed through microscopy and microanalysis of the produced Moiré pattern, assisted with modeling and analyzing the underlying mechanism between the Moiré pattern and the rotation angle. Our work provides experimental and theoretical support for future construction of Moiré-superlattice structure for a wide range of MXene phases and is undoubtedly promoting the development of MXene materials in the field of energy storage.

It is challenging for precise governing of electronic configuration of the individually-atomic catalysts toward optimal electrocatalysis, as d-band configuration of a metal center determines the adsorption behavior of reactive species to the center in oxygen reduction reaction (ORR). The addition of Cu atom modifies the d-band center position of Fe central atom, thus strengthening the d–π* orbital interactions. Herein, FeCu-NC catalyst in the nitrogen-doped carbon (NC) support containing individual dual-metal CuN₄/FeN₄ sites was prepared by the surface confinement strategy of zeolitic imidazolate framework (ZIF), treated as a model catalyst. Experimentally and theoretically co-verified dual-metal CuN₄/FeN₄ sites highly dispersed in the NC support, enable transferring more electrons from FeN₄ sites to *OH intermediates, thereby accelerating the desorption process of *OH species. Superior to those commercial Pt/C, Our FeCu-NC catalyst exhibited extraordinary ORR activity (with a E_1/2 as high as 0.87 V) and cycling stability in 0.1 M KOH electrolyte, and thereof demonstrated excellent discharge performance in zinc-air batteries. Our construction of dual-atom catalysts (DACs) provides a strategy for atom-by-atom designing high-efficiency catalysts via orbital regulation.

MXene quantum dots (MQDs) offer wide applications owing to the abundant surface chemistry, tunable energy-level structure, and unique properties. However, the application of MQDs in electrochemical energy conversion, including hydrogen evolution reaction (HER), remains to be realized, as it remains a challenge to precisely control the types of surface groups and tune the structure of energy levels in MQDs, owing to the high surface energy–induced strong agglomeration in post-processing. Consequently, the determination of the exact catalytically active sites and processes involved in such an electrocatalysis is challenging because of the complexity of the synthetic process and reaction conditions. Herein, we demonstrated the spontaneous evolution of the surface groups of the Ti₂CT_x MQDs (x: the content of O atom), i.e., replacement of the -Cl functional groups by O-terminated ones during the cathode reaction. This process resulted in a low Gibbs free energy (0.26 eV) in HER. Our steady Ti₂CO_x/Cu₂O/Cu foam systems exhibited a low overpotential of 175 mV at 10 mA cm⁻² in 1 M aq. KOH, and excellent operational stability over 165 h at a constant current density of −10 mA cm⁻².

The interaction between electrode materials and charge carriers is one of the central issues dominating underlying energy storage mechanisms. To address the notoriously significant volume changes accompanying intercalation or formation of alloy/compounds, we aim to introduce and utilize a weak, reversible Fe–N interaction during the (de)intercalation of ammonium ions (NH₄⁺) within iron(Ⅲ) hexacyanoferrate (FeHCF), inspired by manipulating the electrostatic adsorption between N and Fe in the early stages of ammonia synthesis (Bosch-Harber Process, Chemical Engineering) and steel nitriding processes (Metal Industry). Such strategy of switching well-balanced Fe–N interaction is confirmed in between the nitrogen of ammonium ions and high-spin Fe in FeHCF, as observed by using X-ray absorption spectroscopy. The resulting material provided an extremely stable energy storage (58 mAh g⁻¹ after 10000 cycles at current density of 1 A g⁻¹) as well as high-rate performance (23.6 mAh g⁻¹ at current density of 10 A g⁻¹).

Energy density can be substantially raised and even maximized if the bulk of an electrode material is fully utilized. Transition metal oxides based on conversion reaction mechanism are the imperative choice due to either constructing nanostructure or intercalation pseudocapacitance with their intrinsic limitations. However, the fully bulk utilization of transition metal oxides is hindered by the poor understanding of atomic-level conversion reaction mechanism, particularly it is largely missing at clarifying how the phase transformation (conversion reaction) determines the electrochemical performance such as power density and cyclic stability. Herein, α-Fe₂O₃ is a case provided to claim how the diffusional and diffusionless transformation determine the electrochemical behaviors, as of its conversion reaction mechanism with fully bulk utilization in alkaline electrolyte. Specifically, the discharge product α-FeOOH diffusional from Fe(OH)₂ is structurally identified as the atomic-level arch criminal for its cyclic stability deterioration, whereas the counterpart δ-FeOOH is theoretically diffusionlesslike, unlocking the full potential of the pseudocapacitance with fully bulk utilization. Thus, such pseudocapacitance, in proof-of-concept and termed as conversion pseudocapacitance, is achieved via diffusionless-like transformation. This work not only provides an atomic-level perspective to reassess the potential electrochemical performance of the transition metal oxides electrode materials based on conversion reaction mechanism but also debuts a new paradigm for pseudocapacitance.