Green Energy & Environment最新文献

Heteroatom-doped carbon-based transition-metal single-atom catalysts (SACs) are promising electrocatalysts for oxygen reduction reaction (ORR). Herein, with the aid of hierarchically porous silica as hard template, a facile and general melting perfusion and mesopore-confined pyrolysis method was reported to prepare single-atomic Fe/N–S-doped carbon catalyst (FeNx/NC-S) with hierarchically porous structure and well-defined morphology. The FeNx/NC-S exhibited excellent ORR activity with a half-wave potential (E_1/2) of 0.92 V, and a lower overpotential of 320 mV at a current density of 10 mA cm⁻² for OER under alkaline condition. The remarkable electrocatalysis performance can be attributed to the hierarchically porous carbon nanospheres with S doping and high content of Fe-Nx sites (up to 3.7 wt% of Fe), resulting from the nano-confinement effect of the hierarchically porous silica spheres (NKM-5) during the pyrolysis process. The rechargeable Zn-air battery with FeNx/NC-S as a cathode catalyst demonstrated a superior power density of 194.5 mW cm⁻² charge–discharge stability. This work highlights a new avenue to design advanced SACs for efficient sustainable energy storage and conversion.

Lithium metal anode is almost the ultimate choice for high-energy density rechargeable batteries, but its uneven electrochemical dissolution-deposition characteristics lead to poor cycle stability and lithium dendrites safety problems. The fundamental solution to the problems is to interfere electrodeposition process of lithium metal so that it can be carried out reversibly and stably. In this work, an inverse-opal structured TiO₂ membrane with a thickness of only ∼1 μm is designed to regulate the electrodeposition behavior of lithium metal, in which the ordered channels homogenize mass transfer process, the anatase TiO₂ walls of the ion channels reduce desolvation barrier of solvated lithium-ions, and the spherical cavities with a diameter of ∼300 nm confine migration of the adsorbed lithium atoms during electrocrystallization to diminish overpotential of lithium. These systematic effects cover and essentially change the whole process of electrodeposition of lithium metal and eliminate the possibility of lithium dendrite formation. The as-obtained lithium metal electrode delivers a Coulombic efficiency of 99.86% in the 100th cycle, and maintains a low deposition overpotential of 0.01 V for 800 h.

To meet the practical demand of wearable/portable electronics, developing high-efficiency and durable multifunctional catalyst and in-situ assembling catalysts into electrodes with flexible features are urgently needed but challenging. Herein, we report a simple route to fabricate bendable multifunctional electrodes by in-situ carbonization of metal ion absorbed polyaniline precursor. Alloy nanoparticles encapsulated in graphite layer are uniformly distributed in the N-doping carbon nanorod skeleton. Profiting from the favorable free-standing structure and the cooperative effect of metallic nanoparticles, graphitic layer and N doped-carbon architecture, the trifunctional electrodes exhibit prominent activities and stability toward HER, OER and ORR. Notably, due to the protection of carbon layer, the electrocatalysts show the reversible catalytic HER/OER properties. The overall water splitting device can continuously work for 12 h under frequent exchanges of cathode and anode. Importantly, the bendable metal air batteries fabricated by self-supported electrode not only displays the outstanding battery performance, achieving a decent peak power density (125 mW cm⁻²) and exhibiting favorable charge-discharge durability of 22 h, but also holds superb flexible stability. Specially, a lightweight self-driven water splitting unit is demonstrated with stable hydrogen production.

Developing efficient electrocatalysts for converting dinitrogen to ammonia through electrocatalysis is of significance to the decentralized ammonia production. Here, through high-throughput density functional theory calculations, we demonstrated that the interfacial modulation of hexagonal boron nitride/graphene (hBN-graphene) could sufficiently improve the catalytic activity of the single transition metal atom catalysts for nitrogen reduction reaction (NRR). It was revealed that Re@hBN-graphene and Os@hBN-graphene possessed remarkable NRR catalytic activity with low limiting potentials of 0.29 V and 0.33 V, respectively. Furthermore, the mechanism of the enhanced catalytic activity was investigated based on various descriptors of the adsorption energies of intermediates, where the synergistic effect of hBN and graphene in the hybrid substrate was found to play a key role. Motivated by the synergistic effect of hybrid substrate in single-atom catalysts, a novel strategy was proposed to efficiently design dual-atom catalysts by integrating the merits of both metal components. The as-designed dual-atom catalyst Fe-Mo@hBN exhibited more excellent NRR catalytic performance with a limiting potential of 0.17 V, manifesting the solidity of the design strategy. Our findings open new avenues for the search of heterostructure substrates for single-atom catalysts and the efficient design of dual-atom catalysts for NRR.

Ammonia (NH₃), a carbon-free hydrogen carrier, is an important commodity for the food supply chain owing to its high energy capacity and ease of storage and transport. The Haber–Bosch process is currently the favored industrial method for large-scale ammonia production but requires energy-intensive and sophisticated infrastructure which hampers its utilization in a sustainable and decentralized system of manufacture. The electrochemical nitrogen reduction reaction (eNRR) at ambient conditions holds great potential for sustainable production of ammonia using electricity generated from renewable energy sources such as solar and wind. However, this approach is limited by a low rate of ammonia production with high overpotential and the competing hydrogen evolution reaction (HER). For a better understanding and utilization of eNRR as a sustainable process, insight into rational catalyst design and mechanistic evaluations by a theoretically-directed experimental approach is imperative. Herein, recent insights into rational catalyst design and mechanisms, based on intrinsic and extrinsic catalytic activity are articulated. Following the elucidation of basic principles and mechanisms, a framework supplied by theoretical studies that lead to the optimal selection and development of eNRR catalysts is presented. Following a discussion of recently developed electrocatalysts for eNRR, we outline various recently-used theoretical and experimental methodologies to improve the intrinsic and extrinsic catalytic activity of advanced electrocatalysts. This review is anticipated to contribute to the development of active, selective, and efficient catalysts for nitrogen reduction.

Lithium metal anode (LMA) is a promising candidate for achieving next-generation high-energy-density batteries due to its ultrahigh theoretical capacity and most negative electrochemical potential. However, the practical application of lithium metal battery (LMB) is largely retarded by the instable interfaces, uncontrolled dendrites, and rapid capacity deterioration. Herein, we present a comprehensive overview towards the working principles and inherent challenges of LMAs. Firstly, we diligently summarize the intrinsic mechanism of Li stripping and plating process. The recent advances in atomic and mesoscale simulations which are crucial in guiding mechanism study and material design are also summarized. Furthermore, the advanced engineering strategies which have been proved effective in protecting LMAs are systematically reviewed, including electrolyte optimization, artificial interface, composite/alloy anodes and so on. Finally, we highlight the current limitations and promising research directions of LMAs. This review sheds new lights on deeply understanding the intrinsic mechanism of LMAs, and calls for more endeavors to realize practical Li metal batteries.

Ni–Ru bimetallic porous carbon sphere (Ni–Ru@PCS) catalysts were synthesized via formaldehyde-assisted, metal-coordinated crosslinking sol–gel chemistry, in which biomass-derived tannic acid and F127 surfactant were used as carbon precursor and soft template, respectively, and Ni²⁺ and Ru³⁺ were used as cross-linkers. In the developed method, Ni–Ru particles became uniformly dispersed in the carbon skeleton due to strong coordination bonds between metal ions (Ni²⁺ and Ru³⁺) and tannic acid molecules and bimetal interactions. The as-synthesized Ni–Ru_10:1@PCS catalyst with a loading Ni:Ru mole ratio of 10:1 was applied for the selective hydrogenation of glucose to sorbitol, and provided 99% glucose conversion with a sorbitol selectivity of 100% at 140 °C in 150 min reaction time and exhibited good stability and recyclability in which sorbitol yield remained at 98% after 4 cycles with little or no metal agglomeration. The catalyst was applied to glucose solutions as high as 20 wt% with 97% sorbitol yields being obtained at 140 °C in 20 h. The developed bimetallic porous carbon sphere catalysts take advantage of sustainably-derived materials in their structure and are applicable to related biomass conversion reactions.

In this work, a novel heterojunction composite Ag₂S/KTa_xNb_1-xO₃ was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTa_xNb_1-xO₃ and the Ag₂S content were optimized. The best 0.5% Ag₂S/KTa_0.5Nb_0.5O₃ (KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag₂S. Under simulated sunlight, the NH₃ generation rate of 0.5% Ag₂S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0. XRD, XPS, and TEM analysis revealed that Ag₂S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag₂S/KTN heterojunction established a type-II band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag₂S/KTN composite exhibited higher NH₃ generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling.