SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-026-4369-1
Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries for large-scale energy storage due to sodium's abundance and low cost. Among cathode materials, polyanionic compounds like Na3V2(PO4)2O2F (NVPOF) offer high energy density and dual voltage plateaus at ~3.6 and 4.0 V, but suffer from low electronic conductivity and sluggish Na+ diffusion. Here, we report a dual-modulation strategy combining high-valence Nb5+ doping and polydopamine-derived carbon coating to synthesize Na3V1.94Nb0.06(PO4)2O2F-C (NVPOF-Nb-C) via a hydrothermal route. X-ray diffraction and Rietveld refinement confirm that Nb5+ doping induces slight lattice expansion without altering the tetragonal I4/mmm framework. Density functional theory calculations reveal that Nb5+ doping optimizes the crystal structure and reduces the Na+ diffusion barrier, while the uniform carbon coating enhances electron transport. Consequently, NVPOF-Nb-C exhibits remarkably improved electrochemical performance, including high reversible capacity, excellent rate capability, and ultralong cycling stability. In a full cell with hard carbon anode, it delivers a high energy density of 487.2 Wh kg−1 at 1C and retains 91.51% capacity after 3000 cycles at 20C. This work provides a synergistic strategy to overcome the intrinsic limitations of polyanionic cathodes for practical SIB applications.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3608-8
Polymeric carbon nitride (PCN) is a promising photocatalyst for H2O2 production due to its visible-light response, low cost, and high selectivity for the two-electron oxygen reduction reaction (ORR). However, its H2O2 yield is limited by narrow light absorption, low charge separation efficiency, and insufficient active sites. Here, crystalline poly(heptazine imide) (PHI)-based carbon nitride with highly dispersed In sites and N defects was prepared via an ionothermal method using LiCl/KCl molten salts. The large π-conjugated system and N defects enhance visible-light harvesting. Remaining K+ ions in nitrogen cavities act as interlayer electron channels, while N defects induce asymmetric charge distribution on the heptazine network, promoting interlayer and in-plane charge separation and transfer. In sites accelerate charge transfer dynamics and serve as active sites for ORR. The synergistic effect of metal modification and defect engineering boosts electron delocalization, significantly improving photocatalytic activity. The H2O2 production rate of 10InPHI reaches 15.3 mmol g−1 h−1 via a two-step single-electron ORR pathway, underscoring the potential of modified carbon nitride for efficient H2O2 photosynthesis.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3746-x
The polyanionic compound Na3V2(PO4)2O2F (NVPOF) possesses a stable three-dimensional framework, high theoretical specific capacity, and favorable operating voltage, yet its sluggish Na+ diffusion kinetics and low electronic conductivity impede industrial application. This study proposes a dual regulation strategy combining carbon coating and heat treatment temperature to synergistically enhance crystallinity and electrochemical performance. NVPOF@C-400 and NVPOF@C-600 were synthesized via in-situ dopamine hydrochloride coating followed by heat treatment at 400 °C and 600 °C, respectively. Carbon coating at 600 °C significantly improved crystallinity and increased electronic conductivity by three orders of magnitude through the carbon layer's conductive network. The ~4.5 nm carbon layer effectively suppressed abnormal grain growth and secondary crystallization aggregation at high temperatures, maintaining uniform particle size of approximately 0.36 μm, which shortens Na+ diffusion pathways and prevents ion transport obstruction. Consequently, NVPOF@C-600 delivered a high discharge capacity of 102.5 mAh g−1 at 20 C and retained 96.5% capacity after 10,000 cycles. In a full-cell configuration with hard carbon (HC), NVPOF@C-600//HC achieved an impressive 89.3% capacity retention after 9,000 cycles. This work provides critical insights for practical implementation of high-performance NVPOF cathodes in sodium-ion batteries.
Environmental Chemistry•2026•DOI: 10.7524/j.issn.0254-6108.2024083002
Selenium (Se) is an essential trace element for human health, and dietary intake through Se-rich crops is the primary route. However, total soil Se content does not directly reflect the bioavailability to plants, which depends largely on soil available Se. This study, conducted in Shipai Town, Longshan County, Hunan Province, used 1:50,000 land quality geochemical survey data to investigate factors influencing the Se bioaccumulation coefficient in maize kernels. Soil pH, CaO, and MgO were identified as significantly positively correlated with the bioaccumulation coefficient and were selected as proxies for soil available Se. A random forest (RF) model was developed to predict maize grain Se content and assess the feasibility of cultivating Se-rich maize in low-Se farmland. Results showed that although soil Se was deficient, 53.64% of maize grain samples met the Se-rich product standard (0.02–0.30 mg·kg−1). Compared with multiple linear regression, the RF model exhibited higher accuracy and reliability. The RF model predicted that 40.91% of farmland in the study area is suitable for natural Se-rich maize cultivation, representing a 25.86% increase over the area identified by soil total Se alone. This study provides a novel methodological framework for planting natural Se-rich maize in Se-deficient regions, validating the potential for such cultivation.