Marine CO2 hydrate sequestration has emerged as a promising strategy for large-scale and long-term carbon storage. Rapid conversion of liquid CO2 into negatively buoyant hydrates is a key challenge, especially in the positive-buoyancy zone. Jet injection of liquid CO2 offers a feasible route to accelerate hydrate formation and aligns with the technical pathway toward large-scale CO2 storage. In this study, the jet characteristics and hydrate formation behavior of liquid CO2 in high-pressure water were investigated under non-hydrate-forming conditions (6.5 MPa, 10 °C) and hydrate-forming conditions (6.5 MPa, 3 °C), respectively. Panoramic and close-up imaging captured the initial breakup morphology and temporal evolution across five jet instability regimes, confirming their correspondence with the We. Droplet size distributions across these regimes were also characterized, showing an overall decrease with increasing Weber number (We), while the transitional range (We ≈ 22‒669) exhibited significant droplet enlargement and reduced uniformity, with the coefficient of variation (CV) exceeding 75%. Additionally, hydrate nucleation within the jet system remained strongly probabilistic. Atomized jets could induce nucleation on timescales of seconds or even milliseconds, yet high jet velocity alone did not guarantee nucleation. Four typical types of hydrate formation were observed, including the most favorable form, i.e., instantaneously formed self-settling hydrate clusters. Furthermore, high-speed close-up imaging revealed multi-site, millisecond-scale nucleation mechanisms and a three-stage clustering process. These findings demonstrate that liquid CO2 jet injection can rapidly form self-settling hydrates in the positive- buoyancy zone, providing a promising pathway for hydrate-based oceanic CO2 sequestration and contributing to global carbon neutrality.
The selective oxidation of methane (CH4) to methanol (CH3OH) requires efficient C−H activation while limiting product over-oxidation. Here a CO-assisted Pt/CeO2–aqueous Cu tandem system is developed for selective CH4 oxidation in aqueous media. CO adsorbs strongly on Pt and serves as both a surface regulator and a co-reactant in O2 activation. Density functional theory (DFT) calculations predict a downward shift of 0.73 eV in the Pt d-band center on the model Pt(111) surface, indicating a modified adsorption environment. Isotope-labeling and sequential-reaction experiments identify gas-phase O2 as the primary oxygen source incorporated into CH3OH and support a CO-coupled O2 activation process. Mobile aqueous Cu species are proposed to contribute to redox mediation, potentially limiting the accumulation of excess reactive oxygen and suppressing CH3OH overoxidation. Under optimized conditions, the system achieves a CH3OH yield rate of 14.38 mmol/(gcat·h) with 100% CH3OH selectivity among the detected liquid-phase products. This work demonstrates a tandem strategy for independently regulating oxygen activation and product preservation during selective C−H oxidation.
Green hydrogen production by water electrolysis still faces a major gap between excellent laboratory catalyst performance and practical industrial economics. Although significant progress has been made in oxygen evolution reaction (OER) catalysts, improvements in intrinsic activity do not necessarily translate into meaningful cost reductions in real electrolyzer systems. In this review, the “Scale-up Paradox” is discussed from the perspective of the levelized cost of hydrogen (LCOH). Three key engineering challenges that determine industrial performance and cost are highlighted: manufacturing scalability and interfacial stability during electrode scale-up; gas–liquid mass transport limitations under high current densities; and chemical and mechanical degradation under dynamic start–stop operation driven by intermittent renewable electricity. The influence of different optimization strategies on LCOH is further analyzed from a techno-economic perspective. The analysis shows that improving mass transport and extending stack lifetime under dynamic operation can provide much larger economic benefits than simply reducing catalyst material costs. Based on these insights, key design considerations for next-generation industrial OER electrodes are outlined, with emphasis on dynamic durability, scalable manufacturing, efficient mass transport under high-current operation, non-destructive operando diagnostics, and in situ regeneration strategies for industrial electrolyzers. This review aims to establish a techno-economic framework for the development of economically viable gigawatt-scale water electrolysis systems.
The design of an integrated bypass diode employed for hot-spot protection in passivating-contact back-contact (TBC) solar cells involves an inherent tension: the structure must conduct sufficient current under reverse bias to prevent hot-spot formation, yet remain highly resistive under forward bias to avoid degrading power output of cells. However, the complex interplay among band-to-band tunneling (BTBT), trap-assisted tunneling (TAT), interdiffusion, and oxide pinholes that governs reverse conduction and forward leakage remains poorly quantified. A quantitative design framework based on two linked figures of merit (FoM1 and FoM2) is established through comprehensive technology computer-aided design (TCAD) simulations. FoM1 quantifies electrical selectivity as the reverse-to-forward current ratio, while FoM2 translates this selectivity into a geometric design criterion for the overlap region. Systematic parameter exploration reveals phosphorus interdiffusion as the dominant degradation mechanism, suppressing BTBT by over two orders of magnitude even at moderate junction grading. Pinholes exhibit a dual character, enhancing reverse conduction only when interdiffusion is controlled. Design windows ensuring effective hot-spot protection with acceptable forward-bias power loss are established as functions of pinhole density, trap concentration, and interdiffusion depth. A diagnostic methodology distinguishing polysilicon-region degradation from substrate parasitic recombination provides experimentally testable design rules for next-generation TBC cells.
Electrochromism, defined as the reversible, voltage-induced modulation of optical properties arising from redox-driven electronic transitions, has emerged as a cornerstone of adaptive optoelectronic technologies. Although inorganic metal oxides and coordination complexes have long dominated this field, conducting polymers, including polyaniline (PANI), polypyrrole (PPy), and polythiophene (PTh) derivatives, have proven to be versatile alternatives that effectively bridge molecular design with macroscopic functionality. This review provides a systematic overview of recent advances in conducting polymers for electrochromic applications, with an emphasis on the structure–property relationships spanning molecular design, material synthesis, and device integration. Relative to conventional inorganic materials, conducting polymers offer distinct advantages, including tunable bandgaps, multicolor electrochromism, mechanical flexibility, and solution processability, establishing them as a promising platform for next-generation electrochromic technologies. Beginning with molecular structure considerations, this review systematically examines the structural engineering strategies applied to classical conductive polymer (CP) systems (PANI, PPy, and PTh), along with their derivatives and composites. The applicability of various synthetic approaches, including chemical polymerization, electrochemical polymerization, template synthesis, and interfacial polymerization, is critically compared. In addition, the functional coupling mechanisms among the transparent conductive layer, ion storage layer, electrolyte layer, and electrochromic layer are discussed in depth. On this basis, the design principles and application scenarios of transmissive, reflective, and multifunctional integrated devices, including self-powered systems, electrochromic energy storage devices, and electrochromic sensors, are reviewed. To address current challenges related to synthetic controllability, environmental stability, and cycling durability, several promising strategies are proposed, including coordination chemistry modulation, n-type conducting polymers, quasi-solid-state/all-solid-state flexible device architectures, data-driven materials discovery, and circular design principles. Finally, it is highlighted that, driven by the “dual carbon” goals, conducting polymer-based electrochromic materials are progressively evolving toward multifunctional integration, sustainable manufacturing, and intelligent device applications.
