SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4236-8
Electrochemical nitrate reduction (NO3RR) to ammonia offers a sustainable route for nitrogen recovery from wastewater, yet its efficiency is constrained by complex multi-step proton-electron transfers and competitive hydrogen evolution. Here, we report a series of binary cobalt-copper phosphates with precisely tuned Co/Cu ratios, revealing a volcano-type relationship between composition and catalytic activity. The optimized Co0.5Cu1.5(OH)PO4 catalyst, supported on a Ni3Co1OxHy/Ni foam substrate, achieves a Faradaic efficiency of 99.0% for ammonia at a high current density of 200 mA cm−2 in 1 M nitrate electrolyte, with a production rate of 9.18 mg h−1 cm−2 and sustained stability over 200 hours. In-situ ATR-FTIR spectroscopy and density functional theory calculations elucidate a tandem mechanism: Co sites promote water dissociation to generate active hydrogen (H*), while adjacent Cu sites facilitate nitrate adsorption and subsequent hydrogenation steps. This synergistic division of labor lowers the energy barrier for the rate-determining step, effectively suppressing HER and enhancing intrinsic kinetics. The work demonstrates that precise atomic-ratio engineering in dual-site transition metal phosphates provides a viable strategy to overcome activity-selectivity trade-offs in electrocatalytic nitrate-to-ammonia conversion.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4277-1
Two-dimensional (2D) magnetic materials hold promise for next-generation spintronics, yet most exhibit Curie temperatures (Tc) far below room temperature, limiting practical applications. Here, we report the realization of room-temperature ferromagnetism in CuCrSe2 nanosheets via controlled anion removal achieved by post-synthetic vacuum annealing. Raw CuCrSe2 shows a low Tc of ~120 K, whereas annealed CuCrSe2 (A-CuCrSe2) nanosheets exhibit robust ferromagnetic ordering above 300 K. Structural and compositional analyses, including transmission electron microscopy, Raman spectroscopy, and X-ray absorption spectroscopy, confirm that A-CuCrSe2 retains the original layered crystal structure with an estimated Se vacancy concentration of approximately 10%. Magnetic measurements reveal room-temperature ferromagnetism in exfoliated nanosheets, corroborated by magnetic imaging and electric transport measurements. Anomalous Hall effect (AHE) measurements uncover the coexistence of two ferromagnetic phases within the same sample: one with low Tc (~120 K) and another with high Tc (>300 K), indicating spatially heterogeneous magnetic ordering driven by anion removal distribution. Density functional theory (DFT) calculations elucidate the microscopic mechanism, suggesting that Se vacancies modulate the magnetic exchange interactions, enhancing Tc. This work demonstrates that anion modulation is an effective intrinsic strategy to achieve room-temperature ferromagnetism in 2D materials, potentially advancing spintronic applications.
Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202507064
This study investigates pollutant removal characteristics and kinetic behaviors in sewage networks, and analyzes their impact on the carbon-to-nitrogen ratio (C/N, as COD/TN) of influent to wastewater treatment plants. Source water quality sampling at drainage outlets revealed spatial and temporal variations in C/N, with domestic sewage exhibiting higher C/N than industrial sewage, and diurnal peaks reaching 6.92 versus 4.71 during off-peak hours. Using a pilot-scale adjustable sewage network system in Kunshan, experiments were conducted under high (0.491 m·s−1) and low (0.089 m·s−1) flow velocities, monitoring pollutant removal over 144 hours. Pseudo-first-order kinetics were applied to model COD and TN removal. Results showed that COD (including SCOD and PCOD), BOD5, and SS achieved approximately 80% removal within 144 h, with higher removal at low flow velocity. TN, NH3-N, and TP exhibited lower overall removal rates. Kinetic fitting revealed that COD removal rate constants (kCOD) were significantly higher than those for TN (kTN), and both decreased with increasing flow velocity: at low velocity, kCOD=0.0167 h−1 and kTN=0.0029 h−1; at high velocity, kCOD=0.0127 h−1 and kTN=0.0020 h−1. Simulations based on actual source pollutant concentrations indicated that the time for C/N to drop to the denitrification critical value of 4.50 was 12.24 h at high velocity, but shortened to 9.49 h at low velocity. These findings demonstrate that increasing flow velocity effectively retards the decline of C/N. Therefore, regulating network flow velocity to reduce hydraulic retention time is a key strategy for maintaining adequate C/N at the terminal and ensuring denitrification efficiency in wastewater treatment plants.
Journal of Fuel Chemistry and Technology•2026•DOI: 10.1016/S1872-5813(26)60701-3
Hydrodenitrogenation (HDN) is an effective method for removing nitrogen-containing heteroatom compounds from inferior feedstocks, with the core challenge being the development of catalysts that combine low cost and high performance. In this study, a FeZn-supported catalyst was modified by introducing six different metal promoters (La, Ti, Ce, Mn, Mg, and Cr). It was found that Cr exhibited a pronounced promotional effect on HDN performance. The promoting effect of Cr on the FeZn catalyst's activity originates from its electronic interaction with sulfided Fe species, rather than functioning as an independent active site. Specifically, Cr and Zn species act synergistically as electron donors, transferring electron density to the sulfided Fe species, thereby modulating the electronic structure of Fe to render it in an electron-rich state. This increased electronic density weakens the Fe–S bonds in the active phase, promoting their cleavage and facilitating the formation of hydrogenation active sites known as coordinated unsaturated sulfur vacancies (CUS). After introducing 3% Cr, under conditions of 340–380 °C, 4 MPa pressure, and a high weight hourly space velocity (WHSV) of 8.7 h−1, the catalyst's HDN conversion rate for the basic nitrogen compound quinoline increased by 14.5%–19.7% compared to the unmodified catalyst, reaching 81.9% at 380 °C. Furthermore, Cr introduction increased the number of medium-strength Lewis acid sites, which work synergistically with the increased CUS sites to enhance overall hydrogenation activity. Cr addition effectively governs the selectivity of the HDN pathway, with the reaction rate constant for the deep hydrogenation pathway over the FeZn3Cr@GA catalyst reaching 3.2 times that of the unmodified FeZn@GA catalyst. In summary, using Fe as the primary active metal component and regulating its electronic structure through promoters represents an effective approach for designing low-cost, high-performance HDN catalysts.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4103-8
The industrial production of urea through the integrated Haber–Bosch and Bosch–Meiser processes involves high energy consumption and significant CO2 emissions. Given the persistent technical challenges inherent in direct electrocatalytic methods, catalytic systems that enable the thermal coupling of N2 and CO2 under mild conditions represent a promising and sustainable approach to urea synthesis. Herein, we designed MXene-based bimetallic single-cluster catalysts, M1Ru3@Mo2CO2, in which the M1Ru3 cluster is stably anchored on the Mo2CO2 support. Using density functional theory calculations, we systematically evaluated the structural stability and adsorption capabilities of 3d transition metal variants (M = Sc to Zn) toward N2, CO2, and H2. The results demonstrate that Co1Ru3@Mo2CO2 exhibits excellent thermodynamic stability and enables the synergistic activation of N2, CO2, and H2, fulfilling the prerequisite conditions for catalyzing the direct coupling of N2 and CO2 to form urea. Further analysis reveals that Co1Ru3@Mo2CO2 efficiently promotes the direct thermal coupling of N–C into urea under mild conditions via the associative pathway, with the rate-determining step corresponding to the conversion of *NHNH2 → *NH2NH2 with the low energy barrier of 1.16 eV. Under realistic conditions of 780 K and 29 bar, the calculated turnover frequency reaches 1.01 × 10−3 s−1 site−1. The high catalytic performance arises from the ability of the Co1Ru3 bimetallic cluster to precisely modulate charge transfer between support and reaction intermediates. Moreover, the in situ generated NH2 species acts as an autocatalyst for CO2 hydrogenation, while the cluster selectively enhances the electrophilicity of the *CO intermediate, thereby facilitating the nucleophilic attack by *NH2 and ensuring efficient C–N bond formation. The finding of the outstanding performance of Co1Ru3@Mo2CO2 single cluster catalysts could bypass the energy-intensive NH3 synthesis step, reduce overall energy demand, and remain compatible with existing urea production infrastructure, thereby offering significant scientific and technological significance.