72 Search Results

IrO2 is a commonly employed anode catalyst for CO2 electrolysis in membrane electrode assembly (MEA) systems. However, under high current densities, its structural reconstruction leads to activity loss and stability degradation, limiting the industrial viability of CO2 electrolysis. Herein, we demonstrated a confinement reconstruction strategy to precisely regulate the structural evolution during electrolysis. Ethylene glycol serves as a structural modulator, protecting the catalyst surface, suppressing soluble species formation, and promoting ordered structural evolution. Single-atom Ru acts as a stability enhancer, forming robust Ir–O–Ru bridging structures that facilitate an ordered transformation from a 4-fold [RuO4]/[IrO4] to a 6-fold symmetry [RuO6]/[IrO6] octahedralmore » framework, thereby enhancing structural rigidity and long-term stability. As a result, in MEA-based CO2 electrolysis, the catalyst achieves a stable operation at 200 mA cm–2 for 480 h, maintaining a CO selectivity above 80%. Theoretical calculations further elucidate that the enhanced stability originates from the suppression of oxygen vacancy formation, making the lattice-oxygen-mediated mechanism (LOM) potentially less favorable. This work provides insights into the structural evolution of the OER catalysts under high-current-density conditions, paving the way for large-scale CO2 electrolysis commercialization.« less

Plastic imposes a critical threat to the environment, ecosystems and human health, because of low utilization efficiency of plastics. Here, we demonstrate a sustainable highly efficient cascade photocatalysis for upcycle plastics to value-added acetic acid using Fe single atom catalysts (Fe@C3N4 SAC) at ambient conditions. Inspired by Phanerochaete chrysosporium microbial, the defected Fe@C3N4 SAC acts as a as a bifunctional cascade photocatalyst for both Fenton-like and CO2 reduction reactions. During the reaction, hydroxyl radicals (*OH) form and subsequently oxidize plastics into CO2 intermediates. These CO2 intermediates were then photo-reduced to CH3COOH on the same catalyst via cascade photocatalysis. The mechanismmore » was confirmed by in situ multimodal microscopy and spectroscopies, with density functional theory calculations. A state-of-art CH3COOH yield of 63.8 mg h-1 gcat-1 from PVC, 12.7 mg h-1 gcat-1 from PE, 5.4 mg h-1 gcat-1 from PET, and 5.3 mg h-1 gcat-1 from PP were directly obtained under AM1.5G solar irradiation and further validated under real sunlight (~ 0.6 sun), achieving 5.6 mg h-1 gcat-1 from PET, using low-cost Fe@C3N4 SAC in a sealed reactor by enhancing the photon transport and utilization efficiency. The techno-economic analysis shows it is promising to practically mitigate plastic based on broader social welfare assessments.« less

Iron–nitrogen–carbon (Fe–N–C) catalysts are considered the most active platinum‐free alternative for oxygen reduction reaction (ORR), yet the generated reactive oxygen species (ROS) from general mechanistic pathway rapidly impair the ORR activity and stability of Fe–N–C. Herein, we establish and report an ORR pathway‐switching strategy to circumvent ROS generation and fundamentally improve the activity and stability of Fe–N–C via DFT guided catalyst design. The constructed Fe–V atomic pair catalyst (Fe 1 V 1 ‐NC) with N 2 Fe‐N 2 ‐VN 2 configuration enables side‐on adsorption of O 2 and subsequent direct‐breaking of the O═O bond to form O*, thereby avoiding themore » formation of ROS radicals. Importantly, there is intersite electron interaction between FeN 4 and VN 4 , which further boosts the ORR activity. Consequently, Fe 1 V 1 ‐NC exhibits outstanding ORR activity with onset and half‐wave (E 1/2 ) potentials at 1.02 and 0.89 V versus RHE, respectively, in 0.1 M KOH. Record‐high stability is achieved on Fe 1 V 1 ‐NC with a minimal decay in E 1/2 by 16 mV over 50000 cycles, surpassing Fe–N–C counterpart and most of the catalysts reported to date. The Fe 1 V 1 ‐NC‐based zinc‐air battery reported here demonstrates exceptional durability up to 400 h at 10 mA·cm −2 . This work identifies the intrinsic correlation between ORR pathway, activity, and stability, advancing development of stable catalytic systems.« less

NiMoO_x compounds are widely regarded as among the most efficient non-noble metal catalysts for the hydrogen evolution reaction (HER). Nevertheless, understanding the structural evolution under in situ conditions and further enhancing their performance remain key challenges. Herein, we report that single-atom Mo doping in NiO significantly enhances its HER activity, reducing the overpotential to 131 mV at 10 mA cm⁻² compared to undoped NiO. In situ X-ray absorption spectroscopy and Raman spectroscopy reveal that under catalytic conditions, Mo single atoms remain structurally stable, while Ni²⁺ species in NiO are converted to Ni(OH)₂ in alkaline media under the applied working potentialmore » for HER. Notably, this transformation is absent in undoped NiO, indicating that Mo doping promotes the formation of active Ni(OH)₂ sites, which, in turn, accelerate the rate-limiting water dissociation step. These findings provide critical mechanistic insights into the structural evolution of NiMoO_x during alkaline HER and highlight the importance of in situ studies in the development of highly efficient catalysts.« less

The manipulation of ions in complex oxide materials can be used to mimic brain-like plasticity through changes to the resistivity of a neuromorphic device. Advances in the design of more energy efficient devices require improved understanding of how ions migrate within a material and across its interface. We investigate the exchange of oxygen and hydrogen in a model SrCoO_x epitaxial film—a material that transitions between a ferromagnetic metal and antiferromagnetic insulator depending on the oxygen concentration. Changes to the film during ionic liquid gating were measured by in situ synchrotron x-ray techniques as a function of time and gate voltage,more » examining the reversibility of the oxide over one complete gating cycle. We find that the out-of-plane lattice constant and oxygen vacancy concentration of SrCoO_x are largely reversible although changes were observed in the ordered vacancy structure. Our results provide much needed insight into electrolyte-gated phase behavior in the transition metal oxides.« less

Electrocatalytic CO₂ reduction is garnering significant interest due to its potential applications in mitigating CO₂ and producing fuel. However, the scaling up of related catalysis is still hindered by several challenges, including the cost of the catalytic materials, low selectivity, small current densities to maintain desirable selectivity. In this study, Fluorine (F) atoms were introduced into an N-doped carbon-supported single nickel (Ni) atom catalyst via facile polymer-assisted pyrolysis. This method not only maintains the high atom utilization efficiency of Ni in a cost-effective and sustainable manner but also effectively manipulates the electronic structure of the active Ni-N₄ site through Fmore » doping. The catalyst has also been further optimized by controlling the F states, including convalent and semi-ionic states, by adjusting the fluorine sources involved. Consequently, this catalyst with unique structure exhibited comparable electrocatalytic performance for CO₂-to-CO conversion, achieving a Faradaic efficiency (FE) of over 99% across a wide potential range and an exceptional CO evolution rate of 9.5 x 10⁴ h^-1 at -1.16 V vs reversible hydrogen electrode (RHE). It also delivered a practical current of 400 mA cm^-2 while maintaining more than 95% CO FE. Experimental analysis combined with density functional theory (DFT) calculations have also shown that F-doping modifies the electron configuration at the central Ni-N₄ sites. In conclusion, this modification lowers the energy barrier for CO₂ activation, thereby facilitating the production of the crucial *COOH intermediate.« less

Given the growing emphasis on energy efficiency, environmental sustainability, and agricultural demand, there’s a pressing need for decentralized and scalable ammonia production. Converting nitrate ions electrochemically, which are commonly found in industrial wastewater and polluted groundwater, into ammonia offers a viable approach for both wastewater treatment and ammonia production yet limited by low producibility and scalability. Here we report a versatile and scalable solution-phase synthesis of high-entropy single-atom nanocages (HESA NCs) in which Fe and other five metals-Co, Cu, Zn, Cd, and In-are isolated via cyano-bridges and coordinated with C and N, respectively. Incorporating and isolating the five metals intomore » the matrix of Fe resulted in Fe-C5 active sites with a minimized symmetry of lattice as well as facilitated water dissociation and thus hydrogenation process. As a result, the Fe-HESA NCs exhibited a high selectivity toward NH3 from the electrocatalytic reduction of nitrate with a Faradaic efficiency of 93.4% while maintaining a high yield rate of 81.4 m h^-1 mg^-1.« less

High-efficiency and low-cost catalysts for oxygen evolution reaction (OER) are critical for electrochemical water splitting to generate hydrogen, which is a clean fuel for sustainable energy conversion and storage. Among the emerging OER catalysts, transition metal dichalcogenides have exhibited superior activity compared to commercial standards such as RuO₂, but inferior stability due to uncontrolled restructuring with OER. Here, in this study, we create bimetallic sulfide catalysts by adapting the atomic ratio of Ni and Co in Co_xNi_1-xS_y electrocatalysts to investigate the intricate restructuring processes. Surface-sensitive X-ray photoelectron spectroscopy and bulk-sensitive X-ray absorption spectroscopy confirmed the favorable restructuring of transition metalmore » sulfide material following OER processes. Our results indicate that a small amount of Ni substitution can reshape the Co local electronic structure, which regulates the restructuring process to optimize the balance between OER activity and stability. This work represents a significant advancement in the development of efficient and noble metal-free OER electrocatalysts through a doping-regulated restructuring approach.« less

Rare earth elements (REEs), critical to modern industry, are difficult to separate and purify, given their similar physicochemical properties originating from the lanthanide contraction. Here, we systematically study the transport of lanthanide ions (Ln³⁺) in artificially confined angstrom-scale two-dimensional channels using MoS₂-based building blocks in an aqueous environment. The results show that the uptake and permeability of Ln³⁺ assume a well-defined volcano shape peaked at Sm³⁺. This transport behavior is rooted from the tradeoff between the barrier for dehydration and the strength of interactions of lanthanide ions in the confinement channels, reminiscent of the Sabatier principle. Molecular dynamics simulations revealmore » that Sm³⁺, with moderate hydration free energy and intermediate affinity for channel interaction, exhibit the smallest dehydration degree, consequently resulting in the highest permeability. Our work not only highlights the distinct mass transport properties under extreme confinement but also demonstrates the potential of dialing confinement dimension and chemistry for greener REEs separation.« less

Emulating angstrom-scale dynamics of the highly selective biological ion channels is a challenging task. Recent work on angstrom-scale artificial channels has expanded our understanding of ion transport and uptake mechanisms under confinement. However, the role of chemical environment in such channels is still not well understood. Here, we report the anomalously enhanced transport and uptake of ions under confined MoS2-based channels that are ~five angstroms in size. The ion uptake preference in the MoS2-based channels can be changed by the selection of surface functional groups and ion uptake sequence due to the interplay between kinetic and thermodynamic factors that dependmore » on whether the ions are mixed or not prior to uptake. Our work offers a holistic picture of ion transport in 2D confinement and highlights ion interplay in this regime.« less