Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202509035
Aerobic granular sludge (AGS) is an economical and efficient technology, yet its application has been largely confined to sequencing batch reactors (SBRs). This study introduces a novel continuous-flow self-circulating upflow granular sludge bed (Zier) process with separate aeration for treating real domestic wastewater. By regulating operational parameters, the nitrogen removal performance and granular sludge stability were investigated. Under hydraulic retention time of 10 h, self-circulation times of 29–58, and upflow velocity of 11–18 m·h−1, effluent NH4+-N and TN averaged (5±3.4) mg·L−1 and (10±2.8) mg·L−1, respectively, with COD at (30±6.2) mg·L−1. The process maintained sludge stability: mixed liquor suspended solids increased from 5,080 to 6,650 mg·L−1, mean particle size was 209.6 μm, and sludge volume index (SVI) remained at 50–60 mL·g−1. Extracellular polymeric substances (EPS) increased from 26.05 to 68.27 mg·g−1, with proteins (PN) rising from 21.26 to 59.44 mg·g−1 and polysaccharides (PS) from 4.79 to 8.82 mg·g−1, elevating the PN/PS ratio from 4.4 to 6.7. These results confirm that the Zier process preserves granular structure and function in continuous flow. The process demonstrates robust nitrogen removal and offers a novel approach for continuous-flow AGS applications in real wastewater treatment.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3897-6
Decoding the nature of catalytically active sites is an essential prerequisite for the rational design of catalysts for electrochemical H2O2 synthesis, but faces significant challenges, particularly for controversial cobalt single-atom catalysts (Co SACs). Herein, we report trace Co single-atom sites embedded within pyridinic N-rich carbon nanospheres (Co1-NNH3-C), synthesized via a self-assembly coupled surface-coating strategy. The Co1-NNH3-C catalyst demonstrates remarkable H2O2 selectivity (99%) and activity at current density of −3.5 mA cm−2 in 0.1 M H2SO4. Through a combined approach of molecular probe experiments, surface modification, and density functional theory (DFT) calculations, we disclose that pyridinic N, rather than Co single atoms, serves as the direct active site for 2e− oxygen reduction reaction (ORR). The trace Co (0.05 wt%) indirectly facilitated pyridinic N formation during pyrolysis but exhibits negligible direct catalytic involvement. DFT reveals pyridinic N sites optimize OOH intermediate adsorption (ΔG*OOH = 4.0 eV) and minimize reaction overpotential of 0.20 V, enabling scalable H2O2 production (907.5 mmol gcat−1 h−1). This work redefines the role of trace metal in SACs, providing a paradigm for designing metal-induced carbon catalysts for sustainable electrosynthesis for H2O2.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3842-8
The metal-support interactions (MSIs) play a significant role in regulating the electronic structure of metal species on oxide; however, they are often overlooked on carbon-based supports. In this work, hollow nitrogen-doped carbon (H-NC) supported Ru nanoparticles catalyst (Ru/H-NC) was prepared by a solvothermal method using H-NC as support and RuCl3 as precursor. Subsequently, Ru/H-NC was annealed at different temperatures (Ru/H-NC t °C) to adjust the effect of MSIs between H-NC support and Ru nanoparticles. The X-ray photoelectron spectroscopy results showed that the MSIs between Ru species and H-NC support increased with the increase of temperature, and more electrons were transferred from Ru species to H-NC support, thus regulating the valence state of Ru. In hydrogen evolution reaction (HER), the as-synthesized Ru/H-NC 300 °C merely requires overpotential of 35.45 mV to achieve 10 mA/cm2 at low Ru mass loading of 24.03 μg/cm2 on the glassy carbon electrode. The cyclic voltammetry test revealed that the electrochemically active surface area increased first and then decreased with the increasing MSIs. Moreover, electrochemical impedance spectroscopy results showed that HER kinetics of Ru/H-NC t °C catalysts increased first and then decreased with the MSIs enhancement. The density functional theory calculations confirmed that the MSIs effectively optimize the adsorption strength of the key intermediates (H*, HO*) on Ru clusters, and thus greatly improve the catalytic performance of Ru/H-NC in HER.
Chinese Journal of Environmental Engineering•2026•DOI: 10.12030/j.cjee.202509055
Microbial communities are the core functional units in environmental biotechnology. Magnetic field technology, as a non-invasive physical enhancement method, has shown application potential in wastewater treatment and waste resource recovery. Traditional ecological theory posits a positive correlation between species diversity and system function/stability. However, magnetic field enhancement often coincides with improved system performance and decreased microbial diversity, indicating a decoupling. This review systematically explains this phenomenon as the result of magnetic field-driven functional specialization of microbial communities. Magnetic fields act on paramagnetic targets in energy metabolism, including iron-sulfur clusters and cytochromes, alter cell surface physicochemical properties, impose oxidative stress, and select strains with high metabolic flexibility, thereby achieving targeted enrichment of key functional groups such as ammonia-oxidizing bacteria and electroactive bacteria within Proteobacteria. Although such functionally specialized communities have reduced species richness, they exhibit higher energy metabolism efficiency, enhanced electron transfer capacity, optimized interspecies cooperation networks, and strengthened system robustness. These advantages collectively support efficient and stable macroscopic bioprocess performance. This study also discusses potential limitations regarding ecosystem resilience and scenario dependence, and envisions future directions such as quantitative modeling and synergy with magnetic materials to advance magnetic field technology from empirical application to rational design.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3946-2
High energy-density lithium–sulfur (Li–S) batteries with rapid intermediate conversion and forbidden shuttle effect require superior electrocatalysts with tunable catalytic activity. In this protocol, binary FeNi3 alloy nanoparticles homogeneously embedded within carbon nanosheets (FeNi3/CNS) are synthesized to regulate the conversions of sulfur species. Time of flight-secondary mass ion spectroscopy reveals a significantly improved catalytic effect of binary FeNi3 alloy compared to bare Ni, which is confirmed by a larger Li2S amount generated during in situ X-ray diffraction measurement. Further anode characterization validates efficient shuttling suppression and good lithium metal protection. In Li–S batteries, electrochemical tests demonstrate a remarkable rate capability of 852 mAh g−1 at 3.0 C, and outstanding long-term cycle at 1.0 C (639 mAh g−1 after 500 cycles). Even under a wide operation temperature range (−15–60 °C), Li–S batteries exhibit stable cycling with high specific capacities under high current rates. Moreover, Li–S batteries using FeNi3/CNS attain a maximum areal capacity of 5.60 mAh cm−2 under ~4.0 mg cm−2 sulfur. This study highlights the advantages of adopting binary or multi-component metal alloys as electrocatalysts and points out the research directions to advance Li–S batteries into practical applications.