Key Takeaways & Executive Findings
- •• • Quadruple-band synglisis in p-type SnS crystals, achieved via SnS₂ introduction, activates four valence bands and promotes simultaneous energy and momentum convergence, yielding a significant enhancement in power factor (PF = S²σ) and ZT compared to prior triple-band convergence strategies. • • The engineered SnS exhibits an exceptionally wide bandgap of 46 kBT, which is 4.6–7.7 times larger than the conventional 6–10 kBT range deemed ideal for thermoelectric cooling, yet it still functions as a viable refrigeration material, expanding the operational envelope for wide-bandgap thermoelectrics. • • Single-crystal p-type SnS leverages high in-plane carrier mobility and an asymmetric layered structure to support complex electronic band engineering, enabling effective hole doping and multiband interactions that decouple effective mass (m*) from carrier mobility (μ). • • The material system addresses the critical supply-chain risk of tellurium scarcity in commercial Bi₂Te₃ alloys by utilizing earth-abundant, nontoxic, and low-cost tin and sulfur, offering a sustainable alternative for large-scale thermoelectric power generation and Peltier cooling.
China Clean Energy & Battery Radar
Get verified English translations, SEM micrographs & open-access PDF alerts from China's leading state key laboratories delivered to your inbox every Monday at 08:00 EST.
Abstract
Thermoelectric energy conversion is governed by the dimensionless figure of merit ZT = S²σT/κtot, yet decoupling Seebeck coefficient, electrical conductivity, and thermal conductivity remains a persistent challenge. Commercial Bi₂Te₃-based alloys are constrained by tellurium scarcity and high cost, motivating the search for earth-abundant alternatives such as SnSe and SnS. SnS, an analog of SnSe, offers higher elemental abundance and intrinsic low thermal conductivity, but its wide bandgap (Eg ≈ 46 kBT) and poor electrical transport in polycrystalline form have historically limited ZT. Single-crystal p-type SnS exhibits high in-plane carrier mobility and a complex valence band structure with multiple valence band maxima (VBM) separated by small energy offsets (ΔE). Prior work achieved triple-band convergence and triple-band synglisis, but further enhancement requires activating additional valence bands. This study reports the activation of four valence bands and the realization of quadruple-band synglisis in p-type SnS crystals via SnS₂ introduction, which promotes simultaneous convergence of energy and momentum across four valence bands. The resulting band manipulation substantially improves thermoelectric efficiency, yielding high power factor and ZT. Notably, despite an exceptionally wide bandgap of 46 kBT—far exceeding the conventional 6–10 kBT range for thermoelectric cooling—the engineered SnS demonstrates viability as a refrigeration material. These findings establish a pathway for low-cost, earth-abundant, environmentally friendly thermoelectric materials that challenge the dominance of tellurium-based systems.
1. Introduction
Thermoelectric power generation and Peltier cooling enable direct heat-to-electricity conversion, but their efficiency is fundamentally limited by the dimensionless figure of merit ZT = S²σT/κtot. Decoupling the interdependent transport parameters—Seebeck coefficient (S), electrical conductivity (σ), and total thermal conductivity (κtot)—remains a formidable materials science challenge. Commercial deployment has been almost exclusively confined to Bi₂Te₃-based alloys, yet tellurium scarcity and high cost impose severe constraints on scalability. This has driven intensive exploration of earth-abundant, nontoxic alternatives such as Mg₃(Bi,Sb)₂, MgAgSb, and SnSe. Among these, tin sulfide (SnS) is particularly attractive due to its higher elemental abundance and lower cost relative to SnSe, plus intrinsic low thermal conductivity. However, polycrystalline SnS suffers from poor electrical transport arising from its large bandgap, which impedes satisfactory ZT values. Single-crystal p-type SnS offers high in-plane carrier mobility and a complex valence band structure with multiple valence band maxima (VBM) separated by small energy offsets (ΔE), providing a fertile ground for band engineering.
Previous efforts optimized thermoelectric performance through triple-band convergence and triple-band synglisis, but further gains require activating additional valence bands to enhance carrier transport. Recent work by Liu et al. demonstrated that introducing SnS₂ into p-type SnS crystals activates four valence bands and realizes quadruple-band synglisis, significantly improving thermoelectric efficiency by promoting simultaneous convergence of energy and momentum across four valence bands. This breakthrough challenges the conventional wisdom that materials with bandgaps in the 6–10 kBT range are the only viable candidates for thermoelectric cooling; the engineered SnS, with an exceptionally wide bandgap of 46 kBT, still emerges as a viable refrigeration material. The band manipulation strategy lays the foundation for low-cost, earth-abundant, environmentally friendly thermoelectric materials, directly addressing the tellurium supply bottleneck and offering a path to high-performance, sustainable energy conversion.
Loading authentic research manuscript (Pages 1–5)...
JIAO Lei, SUI Jiehe, LIU Zihang (2025). The Remarkable Role of Quadruple-Band Synglisis in High-Thermoelectric Performance Tin Sulfide Crystal. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3338-3
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What specific mechanism enables quadruple-band synglisis in SnS, and how does it improve carrier transport compared to triple-band convergence?
Quadruple-band synglisis is achieved by introducing SnS₂ into p-type SnS crystals, which activates four valence bands and promotes simultaneous convergence of energy and momentum across these bands. This contrasts with triple-band convergence, which only aligns three bands. The additional band involvement increases the density of states near the Fermi level without degrading carrier mobility, thereby enhancing the power factor (PF = S²σ). The synglisis effect decouples effective mass (m*) from carrier mobility (μ), allowing higher Seebeck coefficients and electrical conductivity simultaneously.
The material exhibits a bandgap of 46 kBT, far above the conventional 6–10 kBT range for thermoelectric cooling. How can it still function as a refrigeration material?
Conventional thermoelectric cooling relies on narrow-gap semiconductors to ensure sufficient carrier concentration and bipolar transport. However, the engineered SnS achieves high ZT through band engineering that enhances the power factor and reduces thermal conductivity, compensating for the wide bandgap. The quadruple-band synglisis increases the effective density of states and maintains high carrier mobility, enabling efficient Peltier cooling even with a 46 kBT gap. This expands the operational envelope for thermoelectric materials and challenges the narrow-gap paradigm.
What are the scalability and cost implications of using SnS₂-doped SnS crystals for commercial thermoelectric modules?
SnS and SnS₂ are composed of earth-abundant, low-cost, and nontoxic elements, avoiding the tellurium supply constraints of Bi₂Te₃. Single-crystal growth, however, may pose scalability challenges and higher processing costs compared to polycrystalline materials. The introduction of SnS₂ as a dopant is a straightforward compositional modification, but achieving uniform quadruple-band synglisis across large volumes requires precise control of stoichiometry and thermal history. Cost parity with Bi₂Te₃ will depend on optimizing crystal growth yields and reducing defect densities.
How stable is the quadruple-band synglisis effect under prolonged thermal cycling, and what degradation mechanisms could impair performance?
The stability of the band convergence depends on the structural integrity of the SnS crystal and the dispersion of SnS₂-derived phases. Prolonged thermal cycling may induce phase segregation, SnS₂ precipitation, or microcrack formation, which can disrupt band alignment and increase thermal conductivity. While specific degradation rates are not provided in the extracted text, analogous SnSe systems exhibit performance degradation above 500 K due to oxidation and sublimation. Encapsulation and careful doping control are essential to mitigate these effects.
What are the measured ZT and power factor values for this quadruple-band synglisis SnS, and how do they compare to state-of-the-art Bi₂Te₃?
The extracted text does not provide exact numerical values for ZT or power factor. However, it states that the quadruple-band synglisis significantly improves thermoelectric efficiency, yielding high power factor and ZT. For context, commercial Bi₂Te₃ alloys typically achieve ZT ≈ 1 at room temperature. The SnS system is positioned as a low-cost alternative, but without explicit numbers, direct comparison is premature. Future reports should quantify ZT and PF to assess competitiveness.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.