Peixin Cui

Real-world mixed textile waste streams seriously hinder recycling. Herein, we present a two-step flash Joule heating (FJH) strategy for directly upgrading mixed textile waste into ordered multilayer nano onion-like fullerenes (NOLFs). The interaction between different fibers, termed a “scaffolding effect” involving physical confinement and chemical bonding, was strengthened by the precarbonization (280 °C) treatment. Consequently, the polyester/cotton mixture can be upgraded to NOLFs within 5 s with high quality (I2D/IG = 1.47) and yield (41.6%) at 2000 °C, and this technology can be successfully extended to other textiles and solid wastes (polyamide, straws, etc.). The evolution pathway of carbon atoms leading to the formation of the core pentagonal/hexagonal ring structure in NOLFs was systematically investigated in this work. Moreover, an automated FJH prototype was developed to produce NOLFs with 86.4 g·day–1 continuously, and these NOLFs derived an excellent performance as electrode and lubricant.

Direct selective conversion of methane into high value-added chemical products has long attracted attention in both industry and academia. The production of C₂ oxygenates is especially challenging owing to the requirement for both C–H activation and C–C coupling. Here we report a boron nanosheet-supported Cu single atom with Cu–B₄ sites (Cu-SAs/B), which can effectively catalyse the conversion of methane to acetic acid with 97% selectivity and a high activity of 221.3 mmol g_Cu⁻¹ h⁻¹ without the addition of CO. In situ X-ray absorption fine structure analysis reveals that Cu single atoms undergo reversible ‘switching’ to Cu₄ clusters under CH₄ oxidation conditions, enabling efficient C–H activation and C–C coupling. The switching behaviour is triggered by the presence of H₂O₂, and the coupling occurs between CH₃^* and CHO^* intermediates formed on Cu single atoms and Cu clusters, respectively, as confirmed by in situ spectroscopic techniques. These findings provide a proof of concept for designing highly effective methane oxidation catalysts based on switchable nanocatalysts.

Ammonia electrosynthesis via nitrate reduction offers a sustainable alternative to Haber–Bosch process, and this reaction involves an initial deoxygenation step from NO ₃ ⁻ to *NO ₂ , followed by successive hydrogenation steps to NH ₃ . Previous studies have mainly focused on the hydrogenation steps due to the competitive hydrogen evolution reaction, and overlooked that early‐stage adsorption and activation govern the overall reaction rate. Here we show that modulating the spin state of octahedral Co in Ni‐doped cobalt spinel markedly accelerates nitrate adsorption and activation. The high‐spin HS‐(Co _0.75 Ni _0.25 )Co ₂ O _x delivers a current density of 1.1 A cm ⁻² and achieves an ammonia yield rate of 83.64 mg·h ⁻¹ ·cm ⁻² with a Faradaic efficiency of 97.8% at −0.32 V versus RHE, substantially outperforming its low‐spin counterpart (52.53 mg·h ⁻¹ ·cm ⁻² , 94.8%). Operando characterizations combined with theoretical calculations reveal that high‐spin octahedral Co sites optimize orbital hybridization with nitrate and facilitate subsequent reduction steps. This electronic modulation lowers the Gibbs free energy change of the NO ₃ ⁻ to *NO ₂ step by 1.55 eV, substantially reducing the energetic penalty for the initial nitrate activation. This work elucidates a spin‐state‐dependent mechanism for accelerated nitrate deoxygenation kinetics and establishes spin engineering as an effective strategy to promote rate‐limiting steps in tandem electrocatalysis, enabling industrially relevant ammonia electrosynthesis.

Single-atom catalysts (SACs) are widely considered for large-scale applications due to their exceptional activity, selectivity, and near-unity atom economy, where active-site configuration is critical. Yet how the active site regulates catalytic performance remains incompletely understood. A long-standing example is layered Fe-N-C, which shows a large discrepancy between theoretical predictions and experimental oxygen reduction reaction (ORR) activity, limiting rational design and predictability. Here, guided by X-ray absorption fine structure (XAFS) observations and supported by simulations and machine learning, we identify a stacked bilayer metal-metal coupling (MMC) configuration as an important active-site motif in these catalysts. Without invoking constant-potential treatments or surface hydroxyl coverage, our model, constructed within the standard computational hydrogen electrode (CHE) framework, reproduces the experimental activity and reconciles theory with experiment, supporting MMC as a plausible and important mechanistic contributor to ORR. By constructing and comparing 15 single-layer (SL) and MMC configurations, we quantify how metal-metal coupling strength governs activity and establish a criterion for selecting appropriate modeling strategies based on coupling intensity. Using machine learning and data mining, we further identify local electronic-structure descriptors that enable quantitative structure-activity relationships to guide catalyst design. Finally, we synthesize a series of molecular catalysts featuring bilayer MMC motifs or isolated single-metal sites, thereby experimentally validating the proposed structural motif and its role in ORR characteristics. This discovery provides guidance for the rational design of SACs and highlights that physically faithful active-site modeling is a prerequisite for predictive theory, with transferable implications for electrocatalytic systems beyond ORR.

The thermodynamic and kinetic mismatch between oxidative and reductive half-reactions represents a central barrier in photocatalysis, largely due to the absence of well-defined and functionally differentiated active sites. Herein, we construct Co and Pt redox dual-site catalysts (CoPt RDSCs), featuring nonbonded yet spatially close single atoms anchored on carbon nitride for H₂O₂ photosynthesis, thereby enabling site-specific utilization of photogenerated holes and electrons. The Co sites act as the hole centers that drive the four-electron water oxidation reaction, whereas the Pt sites serve as the electron centers that catalyze the two-electron oxygen reduction reaction, each lowering the thermodynamic barrier of its respective half-reaction. Crucially, the proximity of these electronically decoupled sites enables the directed migration of the oxidation products (O₂ and H⁺) generated at Co sites to neighboring Pt sites, establishing an internal redox-coupling pathway that accelerates the overall reaction kinetics. Multidimensional in situ spectroscopy, transient photodynamics, and theoretical analyses confirm that each half-reaction proceeds on the designated site independently yet synergistically. Consequently, the CoPt RDSCs achieve a 19.33% apparent quantum efficiency at 420 nm and a 1.46% solar-to-chemical conversion efficiency for H₂O₂ synthesis in pure water, outperforming most of the reported photocatalysts under comparable conditions. Spatial engineering of redox active sites establishes a general design principle for constructing high-performance photocatalysts capable of coordinating oxidative and reductive transformations.

The formation and transformation of ferrihydrite-cadmium (Fh-Cd) coprecipitates play a critical role in controlling the mobility and bioavailability of Cd in soils. However, the impact of biochar particles (BCs), which are widely applied to agricultural soils, on the transformation of metastable Fh-Cd coprecipitates remains unclear. Herein, we investigated Cd behavior during the aging of Fh-BCs-Cd coprecipitates synthesized by using different BCs: pristine BC, graphitized BC (BC_P), BC enriched with oxyl groups (BC_O), and ash-removed BC (BC_M). The incorporation of pristine BC, BC_P, and BC_O significantly reduced the transformation rates (K) of coprecipitates (K = 0.06-0.22 × 10^-2 day^-1). In contrast, Fh-BC_M-Cd (K = 0.53 × 10^-2 day^-1) underwent a similar transformation to Fh-Cd (K = 0.71 × 10^-2 day^-1), forming hematite with the {104} facet and goethite with the dominant facet of {110} and incorporating 11.61% of Cd into these minerals. As explored by FTIR, XAFS, and DFT calculations, SiO₂, the dominant component in BC ash, was a key factor in inhibiting the transformation of Fh-BCs-Cd coprecipitates and suppressing Cd redistribution. This work highlights the inhibition of amorphous SiO₂ in incorporated BCs on the transformation of Fh-BCs-Cd coprecipitates, providing deeper insight into Cd behavior in BC-amended agricultural soils.

Amorphous nanomaterials with identical compositions can possess distinct atomic structures, which significantly influence their performance, underscoring the importance of phase engineering in amorphous nanomaterials. However, the high Gibbs free energy and complex structures associated with their disordered atomic arrangements pose a significant challenge to the phase engineering of amorphous nanomaterials. Herein, we achieved phase engineering of atomically dispersed Fe-doped amorphous RuO_x nanosheets (A-Fe₁/RuO_x NSs) through amorphous-amorphous transition strategies. Specifically, as confirmed by X-ray absorption fine structure measurements, the Fe coordination environment in A-Fe₁/RuO_x NSs was regulated from FeO₄ tetrahedral to FeO₆ octahedral, driven by amorphous-amorphous transition, resulting in two distinct Ru-Fe pair configurations of A-Fe₁/RuO_x NSs: one with a connected tetrahedral FeO₄-octahedral RuO₆ configuration and the other one with a connected octahedral FeO₆-octahedral RuO₆ configuration. Density functional theory calculations demonstrated that the structure differences of the Ru-Fe pair efficiently regulated the adsorption mode of the O₂ molecules from top adsorption to bridge adsorption on an amorphous surface. Consequently, the A-Fe₁/RuO_x NSs with a connected tetrahedral FeO₄-octahedral RuO₆ configuration exhibited an enhanced formation of superoxide radicals during oxidative dehydrogenation reactions, resulting in remarkable catalytic activity in the synthesis of indole, indole derivatives, and quinoline.

Cadmium bioavailability is sensitive to redox fluctuations, with its fate linked to the coupled dynamics of Fe, S, and C. This study examines the behavior of Cd-loaded ferrihydrite (Fh) with/without organic matter (OM) undergoing S(-II)-induced reduction followed by O₂-induced reoxidation. During sulfidation, S(-II) was fully consumed, and Fh was partially reduced to Fe(II) species, with some OM released from the Fh surface. Meanwhile, Cd initially adsorbed on Fh was completely converted to CdS, regardless of Cd loading or the presence of OM. Upon reoxidation, Fe(II) species were reoxidized to Fe(III) oxides, which recaptured OM, while solid-phase S(-II) was oxidized to S⁰ and sulfate. Concurrently, partial oxidation of CdS occurred, mainly driven by H₂O₂ generated during Fe(II) oxidation, with minor contributions from ^•OH and O₂, but OM inhibited CdS oxidation, primarily by scavenging H₂O₂. Released Cd from CdS oxidation was predominantly readsorbed on Fe(III) oxides. Additionally, released Cd was partially structurally incorporated into newly formed Fe(III) oxides while some CdS was encapsulated within Fe(III) oxide aggregates. However, OM interactions with Fe(III) oxides reduced the formation of these Cd species. These findings provide insights into the molecular-scale mechanisms governing Cd dynamics in redox-dynamic environments.