Linghan Lan

The cathodic oxygen reduction reaction (ORR) represents a critical bottleneck in the practical performance of direct formate fuel cells (DFFCs), while the reliance on costly platinum catalysts impedes their widespread commercialization. In this study, we report the facile synthesis of coral branch-like porous Fe-N-C electrocatalysts employing a covalent organic framework (COF) as the support matrix and iron phthalocyanine (FePc) as the source of Fe and N. By modulating the FePc to COF mass ratio, the optimized catalyst, designated FePc1@COF5, exhibits an interconnected coral-shaped porous carbon architecture featuring homogeneously dispersed Fe–Nₓ active sites alongside in situ generated Fe2N and Fe3C nanocrystals. Comprehensive structural analyses reveal a high density of carbon defects and abundant pyridinic nitrogen and Fe–Nₓ moieties resulting from moderate FePc incorporation. Electrochemical evaluation via rotating disk electrode measurements demonstrates that FePc1@COF5 delivers superior ORR performance, with an onset potential of 0.929 V and a half-wave potential of 0.862 V versus the reversible hydrogen electrode (RHE), outperforming commercial 20 wt% Pt/C catalysts. The ORR proceeds predominantly through a four-electron transfer pathway and is characterized by a low Tafel slope of 27.62 mV dec⁻¹, indicative of rapid reaction kinetics. Electrochemical impedance spectroscopy further confirms reduced charge transfer and mass transport resistances. When employed as the air cathode in a membrane-less DFFC configuration, FePc1@COF5 achieves a peak power density of 24.9 mW cm⁻², surpassing that of the Pt/C cathode. This straightforward synthetic approach offers a promising route for the development of cost-effective, high-performance COF-based non-noble metal ORR catalysts suitable for application in DFFCs.

Thin film boiling is widely recognized as an effective strategy for thermal management of high-power density devices. In this work, a bionic canal system foam metal wick (BCFW), inspired by the canal system of Callyspongia plicifera, is presented. This aluminum based and, cost- effective porous composite structure is fabricated via a concise three- step process combining vacuum diffusion bonding, laser etching, and anodization. The BCFW enhances liquid replenishment and capillary pressure during phase-change heat transfer. Visualized thin-film boiling experiments under antigravity conditions confirm its high efficiency and reliability. A critical heat flux (CHF) as high as 331.52 W/cm² was achieved by the G0.5-W0.5 specimen, while a maximum heat transfer coefficient (HTCmax) of 104.34 kW/(m²·K) was attained by the G0.25-W0.5 specimen at a heat flux of 288.69 W/cm². Analysis of capillary transport and vapor–liquid dynamics reveals that the unique canal system structure establishes unidirectional hydrodynamic pathways, enabling the coexistence of sustained capillary liquid supply and favorable thin-film boiling. Optimal CHF arises from smaller, denser grooves (G0.5-W0.5), which provide abundant nucleation sites while preserving a continuous pore network. The highest HTCmax corresponds to a groove-to-wall width ratio of 1:2 (G0.25-W0.5), which more effectively triggers thin-film boiling. Further, this technological pathway offers an ideal core component for realizing two phase thermal management solutions that are highly efficient, reliable, cost effective, and environmentally friendly in large scale applications.

Industrial-scale gas evolution reactions (GERs) are central to energy conversion and storage technologies, yet are often hindered by catalyst delamination and performance degradation caused by rapid and continuous bubble detachment under high current densities. Inspired by the rammed earth walling technique of ancient China, we constructed a porous network coupled with a island-shaped catalyst layer (CL) via a two-step electrodeposition strategy, achieving dual-interfacial mechanical optimization through network-island cooperativity. Experimental investigations revealed that the porous network mimicked the wooden reinforcing bar to provide continuous rigid support, realizing significant structural reinforcement at the substrate-CL interface while effectively suppressing the agglomeration of active components via spatial confinement. Simultaneously, the nanosheet arrays embedded on the island-shaped structure disrupted the continuity of the three-phase contact line of solid-liquid-gas, significantly lowering the CL-bubble interfacial adhesion force. This architectural feature facilitated the rapid and efficient release of bubbles at minimal volumes, preventing prolonged adhesion during bubble growth and mitigating the mechanical damage to the substrate-CL interface caused by subsequent instantaneous violent detachment of bubbles. When applied to the hydrogen evolution reaction (HER), the prepared electrode exhibited low overpotentials of 39 and 191 mV at 100 and 1000 mA cm⁻², respectively, while maintaining stable operation at an ampere-level current density of 1000 mA cm⁻² for over 143 h with negligible performance degradation after 40,000 cycles of cyclic voltammetry test, which significantly outperformed the commercial Pt/C-loaded electrode and the traditional electrode lacking the wooden reinforcing bar architecture, and underscored its broad promise for practical industrial applications.

The rapid expansion of the lithium-ion battery (LIB) industry has resulted in the exponential growth of spent LIBs, underscoring the urgent requirement for the efficient recycling and utilization of spent LIBs. Traditional recycling methods of spent LIBs suffer from high energy and chemical reagent consumption, high pollutant emission, and limited economic viability. Herein, this work proposes a novel biochar-driven multi-stage pyrolysis–roasting–relithiation strategy to achieve energy-saving and green regeneration of spent LiCoO2 (LCO) cathodes. The results show that the introduction of pine sawdust char (PSC) into spent LCO greatly promotes the complete decomposition and reduction of spent LiCoO2 under relatively mild conditions. The subsequent roasting process is able to easily remove the impurities (such as residual PSC) in the pyrolysis products, achieving rather satisfactory recovery rates of Li (95.8%) and Co (99.5%) at optimal conditions during the whole multi-stage process. The sufficient removal of the impurities is beneficial for the final relithiation process, obtaining high-quality regenerated LCO with a well-ordered layered structure, uniform morphology, and freedom from agglomeration, which contributes to its electrochemical performance (170.79 mA h g−1 at 0.1 C) comparable to commercial LCO. Moreover, life cycle and techno-economic assessments indicate that the proposed strategy is an energy-efficient (10.75 MJ kg−1 regenerated LCO) and economical (9.78 $kg−1 regenerated LCO) regeneration route with minimal impact on the environment. This work paves the way for the economical and sustainable recovery technologies of spent LIBs.

In this study, a composite catalytic layer (CL) featuring multiple bubble nucleation sites was constructed by two-step electrodepositions and phosphor doping to realize full lifecycle promotion of bubbles on electrode surface during oxygen evolution reaction (OER). Firstly, the porous nickel framework layer constructed in the first electrodeposition provided ample anchoring sites for nickel-iron layered dual hydroxide precursors in the second electrodeposition, availing active site formation. Secondly, the achieved CL exhibited an abundant micro-nano pore structure. On one hand, this structure enhanced capillary forces, driving the electrolyte deeply into CL pores. This ensured full coverage of the electrolyte on active sites, increasing site exposure while enabling efficient electrolyte renewal. On the other hand, high tortuosity of CL created a spatial confinement effect on dissolved oxygen molecules (DO), slowing DO diffusion into the bulk solution during OER. This generated local supersaturation of DO, providing the necessary condition for bubble nucleation. Additionally, the porous structure with the ample exposed edges and defects formed numerous discontinuous “gas-liquid-solid” triple-phase interfaces, not only creating large-area heterogeneous nucleation sites for bubble formation, but also reducing bubble adhesion forces and facilitating bubble desorption. Finally, Ni2P and Fe2P heterojunctions formed by phosphor doping enhanced CL conductivity and facilitated electron transport during OER. Ultimately, the best NiFeP@NF-skeleton exhibited a superior overpotentials of 306 and 418 mV at 100 and 300 mA cm-2, with low Tafel slope of 90 mV dec-1, charge transfer resistance of 5.14 Ω, and excellent long-term stability, outperforming those of the commercial IrO2-loaded electrode.