Search for: All records

Reconstructing a three-dimensional ocean sound speed field (SSF) from limited and noisy measurements presents an ill-posed and challenging inverse problem. Existing methods used a number of pre-specified priors (e.g., low-rank tensor and tensor neural network structures) to address this issue. However, the SSFs are often too complex to be accurately described by these pre-defined priors. While utilizing neural network-based priors trained on historical SSF data may be a viable workaround, acquiring SSF data remains a nontrivial task. This work starts with a key observation: Although natural images and SSFs admit fairly different characteristics, their denoising processes appear to share similar traits—as both remove random components from more structured signals. This observation allows us to incorporate deep denoisers trained using extensive natural images to realize zero-shot SSF reconstruction, without any extra training or network modifications. To implement this idea, an alternating direction method of multipliers (ADMM) algorithm using such a deep denoiser is proposed, which is reminiscent of the plug-and-play scheme from medical imaging. Our plug-and-play framework is tailored for SSF recovery such that the learned denoiser can be simultaneously used with other handcrafted SSF priors. Extensive numerical studies show that the new framework largely outperforms state-of-the-art baselines, especially under widely recognized challenging scenarios, e.g., when the SSF samples are taken as tensor fibers. The code is available at https://github.com/OceanSTARLab/DeepPnP. 

Redoxmers are organic molecules that serve as charge carriers in redox flow batteries. While these materials are affordable and easy to source, insufficient stability of their charged states (radical ions) remains a challenge. A common reaction of these species is their disproportionation. This reversible reaction yields unstable multiply charged states, shifting the overall charge transfer equilibrium toward the decomposition products. Here we show how kinetic controls can be engineered into a redoxmer molecule to suppress these unwanted charge transfer reactions. This approach is used to transform Wurster’s blue, which is historically the first example of a stable radical ion in organic chemistry, into an exceptionally durable redoxmer molecule that persists over thousands of electrochemical cycles. 

Abstract For global deployment of proton exchange membrane fuel cells, achieving optimal interaction between the components of the cathode active layer remains challenging. Studies addressing the effect of nanoparticle location (inside vs outside of pores) on performance and durability mostly compare porous and nonporous carbon supports, thus coming short of decoupling nanoparticle locality from carbon support effects. To address the influence of nanoparticle locality on performance and durability, new carbon‐supported electrocatalysts with designed and distinct nanoparticle localities are presented. The developed methodology allows to place Pt nanoparticles preferentially inside or outside of the mesopores of conductive carbon supports from materials under development at Cabot Corporation. Synthesis protocols are tuned to control nanoparticle size, crystallinity, and loading; this way the effect of Pt locality can be studied for two experimental carbon supports in isolation from all other parameters. For one carbon support, Pt active surface area and activity are significantly lower when nanoparticles are placed inside the pores. In contrast, for another, more graphitic carbon support, placing nanoparticles inside or outside of the carbon pores produces no appreciable difference in active surface area and performance rotating disk electrode measurements. Given their carefully tailored structure, these catalysts provide a framework for evaluating locality‐performance‐durability relationships. 

Due to their almost unlimited scalability, redox flow batteries can make versatile and affordable energy storage systems. Redox active materials (redoxmers) in these batteries largely define their electrochemical performance, including the life span of the battery that depends on the stability of charged redoxmers. In this study, we examine the effects of expanding the π-system in the arene rings on the chemical stability of dialkoxyarene redoxmers that are used to store positive charge in RFBs. When 1,4-dimethoxybenzene is π-extended to 1,4-dimethoxynaphthalene, a lower redox potential, improved kinetic stability, and longer cycling life are observed. However, when an additional ring is fused to make 9,10-dimethoxyanthracene, the radical cation undergoes rapid O-dealkylation possibly due to increased steric strain that drives methoxy out of the arene plane thus breaking the π-conjugation with O 2p orbitals. On the other hand, the planar structure of 1,4-dimethoxynaphthalene may facilitate second-order reactions of radical cations leading to their neutralization in the bulk. Our study suggests that extending the π-system changes reactivity in multiple (sometimes, opposite) ways, so lowering the oxidation potential through π-conjugation to improve redoxmer stability should be pursued with caution. 

Abstract Developing low‐voltage carboxylate anode materials is critical for achieving low‐cost, high‐performance, and sustainable Na‐ion batteries (NIBs). However, the structure design rationale and structure‐performance correlation for organic carboxylates in NIBs remains elusive. Herein, the spatial effect on the performance of carboxylate anode materials is studied by introducing heteroatoms in the conjugation structure and manipulating the positions of carboxylate groups in the aromatic rings. Planar and twisted organic carboxylates are designed and synthesized to gain insight into the impact of geometric structures to the electrochemical performance of carboxylate anodes in NIBs. Among the carboxylates, disodium 2,2’‐bipyridine‐5,5’‐dicarboxylate (2255‐Na) with a planar structure outperforms the others in terms of highest specific capacity (210 mAh g⁻¹), longest cycle life (2000 cycles), and best rate capability (up to 5 A g⁻¹). The cyclic stability and redox mechanism of 2255‐Na in NIBs are exploited by various characterization techniques. Moreover, high‐temperature (up to 100 °C) and all‐organic batteries based on a 2255‐Na anode, a polyaniline (PANI) cathode, and an ether‐based electrolyte are achieved and exhibited exceptional electrochemical performance. Therefore, this work demonstrates that designing organic carboxylates with extended planar conjugation structures is an effective strategy to achieve high‐performance and sustainable NIBs. 

Abstract Redox‐active polymers (RAPs) are promising organic electrode materials for affordable and sustainable batteries due to their flexible chemical structures and negligible solubility in the electrolyte. Developing high‐dimensional RAPs with porous structures and crosslinkers can further improve their stability and redox capability by reducing the solubility and enhancing reaction kinetics. This work reports two three‐dimensional (3D) RAPs as stable organic cathodes in Na‐ion batteries (NIBs) and K‐ion batteries (KIBs). Carbonyl functional groups are incorporated into the repeating units of the RAPs by the polycondensation of Tetrakis(4‐aminophenyl)methane and two different dianhydrides. The RAPs with interconnected 3D extended conjugation structures undergo multi‐electron redox reactions and exhibit high performance in both NIBs and KIBs in terms of long cycle life (up to 8000 cycles) and fast charging capability (up to 2 A g⁻¹). The results demonstrate that developing 3D RAPs is an effective strategy to achieve high‐performance, affordable, and sustainable NIBs and KIBs. 

Sodium‐on batteries (SIBs) are promising alternatives to lithium‐ion batteries (LIBs) because of the low cost, abundance, and high sustainability of sodium resources. Analogous to LIBs, the high‐capacity electrodes in SIBs always suffer from rapid capacity decay upon long‐term cycling due to the particle pulverization induced by a large volume change. Circumventing particle pulverization plays a critical role in developing high‐energy and long‐life SIBs. Herein, tetrahydroxy‐1,4‐benzoquinone disodium salt (TBDS) that can self‐heal the cracks by hydrogen bonding between hydroxyl group and carbonyl group is employed as a cathode for sustainable and stable SIBs. The self‐healing TBDS exhibits long cycle life of 1000 cycles with a high rate capability up to 2 A g⁻¹due to the fast Na‐ion diffusion reaction in the TBDS cathode. The intermolecular hydrogen bonding has been comprehensively characterized to understand the self‐healing mechanism. The hydrogen bonding‐enabled self‐healing organic materials are promising for developing high‐energy and long‐cycle‐life SIBs.