Abstract Effective emission control requires advanced sorbents that operate efficiently under dilute CO2 concentrations and variable humidities with minimized regeneration energy. However, existing sorbent materials typically incur high operational costs. Here, hydrogel sorbents comprising poly(N-isopropylacrylamide) (PNIPAM) with uniformly distributed triethylenetetramine (TETA) capture sites are developed to enable humidity-enhanced carbon capture and low-temperature regeneration. The hydrogel sorbents exhibit a synergistic moisture-activated capture mechanism, achieving ∼4.1 mmol g–1 CO2 uptake with concurrent water uptake of ∼0.6 g g–1 at 5% CO2 inlet and 70% relative humidity. The gel network enhances oxidative stability and enables regeneration at 50 °C within 30 min, representing a substantial reduction in energy demand. Solar- or Joule-heating-powered regeneration prototype devices are demonstrated to maintain robust stability and durability under continuous operation over 50 cycles. Techno-economic and life-cycle assessments reveal that the hydrogel sorbents offer a promising pathway toward economically viable and environmentally sustainable, decentralized CO2 removal coupled with water recovery.
Abstract Fe-based O3-type Na-layered oxides such as Na[Ni1/3Fe1/3Mn1/3]O2 are attractive cathodes based on earth-abundant elements, yet their high-voltage operation is limited by voltage decay and capacity fading. Here, we identify a distortion−migration cascade initiated by Fe3+ oxidation to Fe4+. The resulting Jahn−Teller distortion of FeO6 octahedra destabilizes Fe within the transition-metal (TM) framework. This destabilization promotes Fe migration into the Na layer and drives irreversible layered to rocksalt-like reconstruction. A stepwise strategy that reduces the Fe content, reinforces the TM−O framework, and blocks Fe migration into the Na layer interrupts this cascade. The optimized cathode delivers 177.96 mAh g−1 with an initial Coulombic efficiency of 94.1% and retains 73.5% capacity after 100 cycles. Experimental and computational analyses reveal continuous structural evolution and suppressed Fe migration. These results establish suppression of distortion-driven Fe migration as a key design principle for stabilizing high-voltage operation in Fe-based Na-layered cathodes.
Abstract Marine carbon dioxide removal via direct ocean capture (DOC) is promising, but current electrochemical DOC systems remain limited by membrane costs and fouling, as well as the difficulty of achieving low energy consumption at industrially relevant current densities. Here, a membraneless electrochemical direct ocean capture (MEC-DOC) platform was developed based on Bi-mediated chloride intercalation chemistry for low-voltage pH-swing operation. Bi-coated carbon-cloth electrodes were characterized, and cell performance was evaluated under galvanostatic operation in unbuffered and bicarbonate-buffered electrolytes using galvano-dynamic and continuous modes. The MEC-DOC operated at 90 A/m2, above several reported DOC operating points and approaching the industrially relevant current-density threshold of 100 A/m2. Proton generation followed the electrode stoichiometry at high Faradaic selectivity, whereas only 59% of the generated acid was delivered to the treated stream. On this measured basis, the continuous mode required 494 kJ/molCO2 (3116 kWh/tonneCO2). These results establish MEC-DOC as a promising membrane-free pathway for scalable DOC.
Abstract The energy-intensive manufacture of nitrogen-based fertilizers such as ammonia (NH3) and urea consumes a significant fraction of the global energy supply. At the same time, widespread accumulation of excess nitrate (NO3–) from agricultural runoff poses serious risks to ecological and human health. These escalating environmental and economic costs highlight a pressing need for more sustainable fertilizer production. Photocatalytic conversion of waste NO3– into NH3 underscores a growing interest in circular low-energy alternatives to the traditional Haber–Bosch process. For example, as the most widely applied nitrogen fertilizer, analogous routes to urea remain critically underdeveloped. We demonstrate the valorization of two abundant and harmful pollutants, nitrate and carbon dioxide (CO2) into urea over a mixture of commercially available TiO2 and CuO photocatalysts. The ability to drive this complex transformation under ambient temperature and pressure using solar energy highlights its potential to lower the energy demand of conventional fertilizer production. These results provide a fundamental platform from which to envision a more sustainable, visible light-driven ammonia/urea synthesis.
Abstract The performance and stability of quasi-2D metal halide perovskite solar cells (PSCs) are strongly governed by the distribution of the low-dimensional phases. Here, we investigate the role of the methylammonium thiocyanate (MASCN) additive in quasi-2D PSCs. XRD, GIWAXS, and transient absorption spectroscopy show that SCN– suppresses the formation of low-n phases and promotes higher-n domains. Spectroscopy and scattering measurements reveal that SCN– coordinates Pb2+ to form intermediate iodoplumbate complexes that appear to assemble into large precursor aggregates, consistent with nucleation intermediates likely promoting higher-n phases. This structural reconfiguration enhances the power conversion efficiency from 5.8 to 13.4%, and retains ∼75% of their initial efficiency after 1000 h under maximum power point tracking and in N2 atmosphere, despite the reduced fraction of the inherently stable low-n phases. These findings demonstrate that the control of the nucleation at the precursor stage is an effective strategy to tune phase distribution and improve efficiency without severely compromising stability in quasi-2D PSCs.
Abstract P2-type layered oxide cathodes feature high median voltage and outstanding cycling stability, but their specific capacity of merely 80 mAh g–1 severely limits practical utility. Conventional P2/O3 biphasic strategies to boost capacity typically sacrifice structural stability or median voltage. In this work, density functional theory calculations identify the thermodynamic phase-ratio boundary for biphasic stability, confirming that limiting sodium-rich O3 phase below 20% suppresses the detrimental O3-P3 transition during cycling. Guided by this, precise transition metal tuning yields an optimal atomically intermixed P2/O3-93 cathode (Na3/4Ni1/3Fe1/12Mn7/12O2). It exhibits pronounced zero-strain behavior, with volume change reduced from 3.7% (O3-type reference) to <1%. It maintains a 3.3 V median voltage, raises capacity by 40% to 112 mAh g–1, and achieves 93% retention after 500 cycles at 1 C. Furthermore, it enables 300 stable cycles in all-solid-state sodium-ion batteries at 30 MPa, offering a viable route for high-performance layered oxide cathodes.
Abstract Understanding how degradation reshapes lithium (de)insertion pathways in high-nickel cathodes is crucial for extending battery lifetime. Here, we integrate operando synchrotron X-ray diffraction (sXRD) with electrode-level transmission X-ray microscopy (TXM) to quantitatively resolve how degradation redistributes lithium accessibility in Ni-rich NCA cathodes. Using a 26-state deconvolution framework, we show that degraded electrodes exhibit nonmonotonic Li-content population evolution: delithiation kinetics are initially suppressed, transiently synchronized, and ultimately diverge, leaving ∼7% discharge-like states and ∼13% intermediate Li-content states at the end of charge. Spatially resolved TXM reveals that this divergence originates from size-dependent accessibility constraints—large particles develop persistent intra-particle state-of-charge gradients, while small particles exhibit pronounced inter-particle disparity. This work establishes a quantitative framework linking bulk Li-content population dynamics to particle-level degradation mechanisms in high-nickel cathodes.
Abstract Mn metal batteries (MnMBs) are promising for stationary applications owing to the low cost and low working potential of Mn anodes. However, developing electrolytes that combine high ionic conductivity with low-overpotential Mn plating/stripping remains challenging because of the trade-off between salt dissociation and desolvation. Herein, we propose a weakly coordinating electrolyte, Mn[B(HFIP)4]2 (HFIP: hexafluoroisopropyl), for advanced MnMBs. The [B(HFIP)4]– anion, featuring full electron delocalization and steric hindrance, promotes complete salt dissociation in low-dielectric-constant ethers, yielding a pure ether-coordinated Mn2+ electrolyte with high ionic conductivity (4.7–8.5 mS/cm at 20 °C) and a wide electrochemical window (>3 V). Weak ether-Mn2+ coordination facilitates desolvation, affording a record-low Mn plating/stripping overpotential (<100 mV at 0.5 mA/cm2) and dendrite-free 3D growth. Coupling Mn anodes with polytriphenylamine or activated carbon cathodes enables quick-charge full cells, demonstrating the potential of anion engineering for high-performance multivalent metal batteries.
Abstract Halide perovskite nanochemistry is evolving at an unprecedented pace, rapidly expanding the scope of these materials from fundamental model systems to platforms with growing impact across both classical and quantum light technologies. In this perspective, we follow perovskite quantum dots (pQDs) from their birth in solution to their fully developed structural and photophysical complexity, highlighting recent advances, offering a critical view on current limitations, and discussing open questions together with possible paths forward. We hope this perspective helps inspire the next generation of ideas, tools, and design principles needed to unlock the full potential of pQDs.
Abstract Achieving an ideal bi-continuous network in organic solar cells requires balancing molecular self-assembly and film-formation kinetics. For strong-interaction polymers like D18, intense backbone interactions often lead to kinetically trapped, disordered states. Here, we present a molecular symmetry-breaking strategy using an asymmetric small-molecule donor, BC-A2O, as a guest regulator. Compared with its symmetric counterpart BC-A4O, BC-A2O features a rigid rhodanine hook and higher liquid-crystal Gibbs free energy difference. This strong thermodynamic drive enables BC-A2O to preferentially anchor onto D18 chains, establishing solution-phase interfacial pre-structuring that seeds a highly ordered fibrillar host network with optimized charge transport channels. Consequently, BC-A2O-based ternary devices achieve a benchmark efficiency of 20.53% (versus 19.46% for the binary baseline) with a fill factor of 81.16%. This work demonstrates the power of small-molecule donors in orchestrating hierarchical assembly for advanced photovoltaics.
Abstract Composite solid polymer electrolytes (CSPEs) have emerged as promising candidates for next-generation lithium metal batteries. However, the spatial evolution of the solid electrolyte interphase (SEI) at solid-state interfaces remains poorly understood despite its critical role in lithium metal stability. Herein, the anion-trapping layered double hydroxide (LDH) is introduced to poly(ethylene oxide)-based CSPEs to regulate Li+ transport and stabilize the lithium/electrolyte interface. The LDH-enhanced electrolyte achieves exceptional cycling stability over 950 h with a lithium electrode and 90.1% capacity retention after 250 cycles in LiFePO4||Li full cells. Operando nano-focus wide-angle X-ray scattering maps the spatial distributions of both the SEI and lithium dendrites at the lithium/electrolyte interface across micron-scale lateral and vertical dimensions. The regulated Li+ flux promotes homogeneous lithium deposition and the formation of a robust, multifunctional SEI, thereby suppressing lithium dendrite growth and stabilizing the interface. This study provides direct visualization of SEI evolution in CSPEs and clarifies its role in dendrite-free all-solid-state lithium metal batteries.
Abstract Unstable low-valent Mn species at LiNi0.5Mn1.5O4 surfaces contribute to surface degradation, yet the electronic mechanism underlying their formation remains insufficiently understood. Through a systematic first-principles investigation across lithiation states, low-index facets, and surface terminations, we find that surface oxygen exhibits enhanced electronic activity and acts as a key mediator of local charge compensation. Surface-specific and delithiation-induced coordination changes, oxygen-vacancy formation, and electrolyte-derived surface-O protonation provide distinct structural, defect, and interfacial perturbations of the local surface-O environment. Collectively, these perturbations converge on local O–Mn charge redistribution, promoting electron accumulation and reduction at neighboring Mn sites and supporting a unified surface-O-mediated pathway for near-surface Mn reduction. A multi-descriptor framework based on local X–O–Mn units further evaluates dopant regulation of oxygen activity and Mn electronic states. More broadly, these mechanistic insights provide an atomistic basis for the mechanism-guided design of spinel cathodes.
Abstract Low-grade industrial waste heat (<300 °C) is abundant yet largely unutilized. Low-temperature steam electrolysis (100–300 °C) could exploit this resource, but progress is limited by the lack of electrolytes that combine high proton conductivity with mechanical and chemical stability. Here, we report a “soggy sand” electrolyte based on ammonium scandium pyrophosphate (NH4ScP2O7) formed directly from phosphoric-acid-rich aqueous solutions. The material comprises a percolated phosphoric acid phase confined within a nanoparticle framework, yielding a viscoelastic solid that enables fabrication of self-standing, gas-tight membranes by simple pressing. The membranes exhibit proton conductivity >10–2 S cm–1 at 150 °C with a tensile strength of ∼7 MPa. Steam electrolysis using the ScP34 membrane operates stably at 0.35 A cm–2 for 150 h, with a cell voltage of ∼1.6 V and a Faradaic efficiency exceeding 95%. This work establishes a design strategy for efficient hydrogen production from low-temperature waste heat.
Abstract Near-infrared tin perovskite light-emitting diodes (PeLEDs) constitute a class of lead-free optoelectronic devices, but their performance suffers from rapid crystallization over a defective hole transport layer underneath the perovskite film. Here, we report a buried-interface kinetic regulation strategy for Cs-rich tin iodide perovskites. The buried interlayer regulated the initial growth of the perovskite film. This regulation delayed the emergence of emissive domains and promoted compact film growth without substantially perturbing the Sn-I framework. Spectroscopic and theoretical analyses reveal interfacial interactions with Sn-related sites, which help suppress defect formation and nonradiative losses. The optimized PeLEDs exhibited near-infrared electroluminescence centered at 945 nm and achieved a peak external quantum efficiency of 8.04%. This work highlights buried-interface kinetic regulation as an effective route toward efficient lead-free near-infrared tin perovskite LEDs.
Abstract Phenoxazine-based compounds are valuable cathode materials owing to their high theoretical capacity and robust redox reversibility. However, insufficient intramolecular charge delocalization destabilizes deeply oxidized states and limits dual-electron transfer. Herein, a “push-pull electronic engineering” strategy is developed by incorporating delocalizing electron-deficient units into the phenoxazine framework to regulate frontier molecular orbitals, extend π-electron delocalization, and stabilize deeply oxidized states. Two isomers, 2,7-di(10H-phenoxazin-10-yl) tribenzo[a,c,i]phenazine-10,15-dione (2,7-DPTBD) and its 3,6-substituted counterpart (3,6-DPTBD), are synthesized. Both materials exhibit reversible dual-electron oxidation. Nevertheless, steric hindrance in 3,6-DPTBD weakens the push-pull interaction and reduces its electrochemical performance. Consequently, 2,7-DPTBD delivers a high energy density of 668 Wh kg–1 at an average discharge potential of 2.56 V. Furthermore, a full cell employing graphite anodes achieves a peak discharge capacity of 211 mAh g–1 and maintains stable cycling over 1000 cycles. Symmetric dual-ion batteries are assembled based on the bipolar characteristics of 2,7-DPTBD, which stably operate for 200 cycles.
Abstract We investigate the nanoscale function of additives used for tin-containing perovskites, using the archetypal FASnI3 (FA = formamidinium). First, we find that the addition of sodium borohydride (NaBH4) is inhomogeneous, with 200–500 nm aggregates forming on the FASnI3 surface. The inhomogeneous distribution of NaBH4 leads to a relatively small (∼1% of the film) amount of reduced perovskite, but the macroscopic properties are dominated by the overwhelming space without any treatment. Upon illumination, more aggregate regions (∼13%) become activated due to reduction of photogenerated I2. On the other hand, when we combine NaBH4 with dipropylammonium iodide (DipI) passivation and illuminate, we observe a much more homogeneous activation effect, which we attribute to denser coverage of NaBH4. We find that the iodine content in FASnI3 films treated with NaBH4 and DipI is 64% less than in those treated with NaBH4 alone. These results underline that the microscale configuration of different additives in tin perovskites is deeply interconnected and it is essential to uncover their chemical reactivity.
Abstract A central challenge in thermoelectric science is to break the intrinsic coupling between charge and heat transport. Herein, we demonstrate that thermally driven interface reconstruction in perovskite-modified skutterudites generates a hierarchical defect architecture that enables simultaneous regulation of electronic and phononic transport. By deliberately integrating point defects, (Pb, In)-rich nanoprecipitates, and multiscale pores into a unified interfacial framework, the reconstructed microstructure enhances carrier-energy selectivity while fostering broadband phonon scattering across multiple length scales. This synergy effectively mitigates the conventional electrical–thermal trade-off, yielding a peak zT of ∼1.76 at 773 K. A seven-couple thermoelectric generator assembled from the optimized material delivers a conversion efficiency of 8.1% under a temperature difference of 452 K. Collectively, these findings establish hierarchical interface reconstruction as a powerful strategy for transport decoupling and highlight defect-architecture engineering as a versatile design principle for thermoelectric energy conversion.
Abstract Surging global demand for lithium-ion batteries (LIBs) creates an urgent imperative to recover critical materials from spent cells at scale. Here we integrate a spinel LiMn2O4 (LMO) ceramic membrane with a bipolar membrane electrodialysis (BMED) architecture enables self-sustaining ion-exchange. Water dissociation at the bipolar membrane generates a continuous proton flux that drives stoichiometric H+/Li+ exchange within the LMO lattice, providing in situ pH regulation without external eluent circulation. By decoupling lithium extraction from the discontinuous intercalation-deintercalation cycles inherent to conventional electrochemical approaches, this design enables continuous ion transport and faster extraction kinetics. Under optimized conditions, the system recovers a lithium recovery flux of 0.255 kg m–2 day–1 with a purity of 99.75%. This experimentally measured rate corresponds to a projected recovery of 254.5 g of Li+ over 24 h using a 1 m2 membrane. This work demonstrates continuous-flow, high-purity lithium recovery and expands ceramic ion-exchange membranes to other critical-mineral separations.
Abstract Electrochemically induced direct air capture (DAC) has emerged as a compelling strategy for mitigating anthropogenic CO2 emissions. However, a critical bottleneck remains the O2 sensitivity of redox-active molecules, which directly degrades both capture efficiency and energy economy. Herein, we report a hybrid flow cell based on the proton-coupled electron transfer (PCET) of tribenzo[a,c,i]phenazine-10,15-dione (TBPDO) that drives pH-swing DAC. The O2 tolerance is enhanced by inducing intramolecular hydrogen bonds in the reduction product (r-TBPDOH2), which kinetically suppress O2 attack by lowering the local electron density at the oxygen center via intramolecular O–H···N═C interactions and extended π-conjugation, as confirmed by density functional theory (DFT) calculations. Consequently, this carbon capture system achieves a release/capture efficiency of 92%, a Coulombic efficiency of 81%, and an energy consumption of 149 kJ mol–1CO2. This work establishes intramolecular hydrogen bonding as a kinetic protection strategy against parasitic O2 oxidation, offering a molecular design principle transferable to other PCET-based electrochemical systems.
Abstract Ultra-long cooling times are the most crucial ingredient for the successful development of a hot-carrier solar cell. Recent experimental reports for metal halide perovskites show the possibility of reaching these relevant values using Sn-based perovskite compositions, due to their low effective mass. In this work, the governing underlying physics is uncovered by investigating the interplay between band filling and the hot phonon bottleneck effect. By using ensemble Monte Carlo simulations and through comparison with time-resolved photoluminescence measurements, it is demonstrated that solely the combination of these two phenomena is sufficient to reproduce ultra-long carrier cooling times. The dependency of band filling on material parameters is analyzed, and it is crucially shown that carriers affected by band filling remain hot in terms of their Fermi–Dirac temperature for the remainder of their energy relaxation period. Our results are important in the discussion regarding the suitability of metal halide perovskites for future HCSC applications, and function as a road-map towards the successful construction of a perovskite-based HCSC.
