Carbon Energy最新文献

Electrochemical reduction of CO₂ to syngas (CO and H₂) offers an efficient way to mitigate carbon emissions and store intermittent renewable energy in chemicals. Herein, the hierarchical one-dimensional/three-dimensional nitrogen-doped porous carbon (1D/3D NPC) is prepared by carbonizing the composite of Zn-MOF-74 crystals in situ grown on a commercial melamine sponge (MS), for electrochemical CO₂ reduction reaction (CO₂RR). The 1D/3D NPC exhibits a high CO/H₂ ratio (5.06) and CO yield (31 mmol g⁻¹ h⁻¹) at −0.55 V, which are 13.7 times and 21.4 times those of 1D porous carbon (derived from Zn-MOF-74) and N-doped carbon (carbonized by MS), respectively. This is attributed to the unique spatial environment of 1D/3D NPC, which increases the adsorption capacity of CO₂ and promotes electron transfer from the 3D N-doped carbon framework to 1D carbon, improving the reaction kinetics of CO₂RR. Experimental results and charge density difference plots indicate that the active site of CO₂RR is the positively charged carbon atom adjacent to graphitic N on 1D carbon and the active site of HER is the pyridinic N on 1D carbon. The presence of pyridinic N and pyrrolic N reduces the number of electron transfer, decreasing the reaction kinetics and the activity of CO₂RR. The CO/H₂ ratio is related to the distribution of N species and the specific surface area, which are determined by the degree of spatial confinement effect. The CO/H₂ ratios can be regulated by adjusting the carbonization temperature to adjust the degree of spatial confinement effect. Given the low cost of feedstock and easy strategy, 1D/3D NPC catalysts have great potential for industrial application.

Catalyst design relies heavily on electronic metal-support interactions, but the metal-support interface with an uncontrollable electronic or coordination environment makes it challenging. Herein, we outline a promising approach for the rational design of catalysts involving heteroatoms as anchors for Pd nanoparticles for ethanol oxidation reaction (EOR) catalysis. The doped B and N atoms from dimethylamine borane (DB) occupy the position of the Ti₃C₂ lattice to anchor the supported Pd nanoparticles. The electrons transfer from the support to B atoms, and then to the metal Pd to form a stable electronic center. A strong electronic interaction can be produced and the d-band center can be shifted down, driving Pd into the dominant metallic state and making Pd nanoparticles deposit uniformly on the support. As-obtained Pd/DB–Ti₃C₂ exhibits superior durability to its counterpart (∼14.6% retention) with 91.1% retention after 2000 cycles, placing it among the top single metal anodic catalysts. Further, in situ Raman and density functional theory computations confirm that Pd/DB–Ti₃C₂ is capable of dehydrogenating ethanol at low reaction energies.

The emergence of Li–Mg hybrid batteries has been receiving attention, owing to their enhanced electrochemical kinetics and reduced overpotential. Nevertheless, the persistent challenge of uneven Mg electrodeposition remains a significant impediment to their practical integration. Herein, we developed an ingenious approach that centered around epitaxial electrocrystallization and meticulously controlled growth of magnesium crystals on a specialized MgMOF substrate. The chosen MgMOF substrate demonstrated a robust affinity for magnesium and showed minimal lattice misfit with Mg, establishing the crucial prerequisites for successful heteroepitaxial electrocrystallization. Moreover, the incorporation of periodic electric fields and successive nanochannels within the MgMOF structure created a spatially confined environment that considerably promoted uniform magnesium nucleation at the molecular scale. Taking inspiration from the “blockchain” concept prevalent in the realm of big data, we seamlessly integrated a conductive polypyrrole framework, acting as a connecting “chain,” to interlink the “blocks” comprising the MgMOF cavities. This innovative design significantly amplified charge-transfer efficiency, thereby increasing overall electrochemical kinetics. The resulting architecture (MgMOF@PPy@CC) served as an exceptional host for heteroepitaxial Mg electrodeposition, showcasing remarkable electrostripping/plating kinetics and excellent cycling performance. Surprisingly, a symmetrical cell incorporating the MgMOF@PPy@CC electrode demonstrated impressive stability even under ultrahigh current density conditions (10 mA cm^–2), maintaining operation for an extended 1200 h, surpassing previously reported benchmarks. Significantly, on coupling the MgMOF@PPy@CC anode with a Mo₆S₈ cathode, the assembled battery showed an extended lifespan of 10,000 cycles at 70 C, with an outstanding capacity retention of 96.23%. This study provides a fresh perspective on the rational design of epitaxial electrocrystallization driven by metal–organic framework (MOF) substrates, paving the way toward the advancement of cutting-edge batteries.

Engineering high-performance and low-cost bifunctional catalysts for H₂ (hydrogen evolution reaction [HER]) and O₂ (oxygen evolution reaction [OER]) evolution under industrial electrocatalytic conditions remains challenging. Here, for the first time, we use the stronger electronegativity of a rare-Earth yttrium ion (Y³⁺) to induce in situ NiCo-layered double-hydroxide nanosheets from NiCo foam (NCF) treated by a dielectric barrier discharge plasma NCF (PNCF), and then obtain nitrogen-doped YNiCo phosphide (N-YNiCoP/PNCF) after the phosphating process using radiofrequency plasma in nitrogen. The obtained N-YNiCoP/PNCF has a large specific surface area, rich heterointerfaces, and an optimized electronic structure, inducing high electrocatalytic activity in HER (331 mV vs. 2000 mA cm⁻²) and OER (464 mV vs. 2000 mA cm⁻²) reactions in 1 M KOH electrolyte. X-ray absorption spectroscopy and density functional theory quantum chemistry calculations reveal that the coordination number of CoNi decreased with the incorporation of Y atoms, which induce much shorter bonds of Ni and Co ions and promote long-term stability of N-YNiCoP in HER and OER under the simulated industrial conditions. Meanwhile, the CoN-YP₅ heterointerface formed by plasma N-doping is the active center for overall water splitting. This work expands the applications of rare-Earth elements in engineering bifunctional electrocatalysts and provides a new avenue for designing high-performance transition-metal-based catalysts in the renewable energy field.

The key to designing photocatalysts is to orient the migration of photogenerated electrons to the target active sites rather than dissipate at inert sites. Herein, we demonstrate that the doping of phosphorus (P) significantly enriches photogenerated electrons at Ni active sites and enhances the performance for CO₂ reduction into syngas. During photocatalytic CO₂ reduction, Ni single-atom-anchored P-modulated carbon nitride showed an impressive syngas yield rate of 85 μmol g_cat⁻¹ h⁻¹ and continuously adjustable CO/H₂ ratios ranging from 5:1 to 1:2, which exceeded those of most of the reported carbon nitride-based single-atom catalysts. Mechanistic studies reveal that P doping improves the conductivity of catalysts, which promotes photogenerated electron transfer to the Ni active sites rather than dissipate randomly at low-activity nonmetallic sites, facilitating the CO₂-to-syngas photoreduction process.

Mo₂C is an excellent electrocatalyst for hydrogen evolution reaction (HER). However, Mo₂C is a poor electrocatalyst for oxygen evolution reaction (OER). Herein, two different elements, namely Co and Fe, are incorporated in Mo₂C that, therefore, has a finely tuned electronic structure, which is not achievable by incorporation of any one of the metals. Consequently, the resulting electrocatalyst Co_0.8Fe_0.2–Mo₂C-80 displayed excellent OER catalytic performance, which is evidenced by a low overpotential of 214.0 (and 246.5) mV to attain a current density of 10 (and 50) mA cm⁻², an ultralow Tafel slope of 38.4 mV dec⁻¹, and long-term stability in alkaline medium. Theoretical data demonstrates that Co_0.8Fe_0.2–Mo₂C-80 requires the lowest overpotential (1.00 V) for OER and Co centers to be the active sites. The ultrahigh catalytic performance of the electrocatalyst is attributed to the excellent intrinsic catalytic activity due to high Brunauer–Emmett–Teller specific surface area, large electrochemically active surface area, small Tafel slope, and low charge-transfer resistance.

Compared with the extensively used ester-based electrolyte, the hard carbon (HC) electrode is more compatible with the ether-based counterpart in sodium-ion batteries, which can lead to improved cycling stability and robust rate capability. However, the impact of salt anion on the electrochemical performance of HC electrodes has yet to be fully understood. In this study, the anionic chemistry in regulating the stability of electrolytes and the performance of sodium-ion batteries have been systematically investigated. This work shows discrepancies in the reductive stability of the anionic group, redox kinetics, and component/structure of solid electrolyte interface (SEI) with different salts (NaBF_4, NaPF₆, and NaSO₃CF₃) in the typical ether solvent (diglyme). Particularly, the density functional theory calculation manifests the preferred decomposition of PF₆⁻ due to the reduced reductive stability of anions in the solvation structure, thus leading to the formation of NaF-rich SEI. Further investigation on redox kinetics reveals that the NaPF₆/diglyme can induce the fast ionic diffusion dynamic and low charge transfer barrier for HC electrode, thus resulting in superior sodium storage performance in terms of rate capability and cycling life, which outperforms those of NaBF₄/diglyme and NaSO₃CF₃/diglyme. Importantly, this work offers valuable insights for optimizing the electrochemical behaviors of electrode materials by regulating the anionic group in the electrolyte.

For the porous-membrane-based osmotic energy generator, the potential synergistic enhancement mechanism of various key parameters is still controversial, especially because optimizing the trade-off between permeability and selectivity is still a challenge. Here, to construct a permeability and selectivity synergistically enhanced osmotic energy generator, the two-dimensional porous membranes with tunable charge density are prepared by inserting sulfonated polyether sulfone into graphene oxide. Influences of charge density and pore size on the ion transport are explored, and the ionic behaviors in the channel are calculated by numerical simulations. The mechanism of ion transport in the process is studied in depth, and the fundamental principles of energy conversion are revealed. The results demonstrate that charge density and pore size should be matched to construct the optimal ion channel. This collaborative enhancement strategy of permeability and selectivity has significantly improved the output power in osmotic energy generation; compared to the pure graphene oxide membrane, the composite membrane presents almost 20 times improvement.

A stable and highly active core-shell heterostructure electrocatalyst is essential for catalyzing oxygen evolution reaction (OER). Here, a dual-trimetallic core-shell heterostructure OER electrocatalyst that consists of a NiFeWS₂ inner core and an amorphous NiFeW(OH)_z outer shell is designed and synthesized using in situ electrochemical tuning. The electrochemical measurements of different as-synthesized catalysts with a similar mass loading suggest that the core-shell Ni_0.66Fe_0.17W_0.17S₂@amorphous NiFeW(OH)_z nanosheets exhibit the highest overall performance compared with that of other bimetallic reference catalysts for the OER. Additionally, the nanosheet arrays were in situ grown on hydrophilic-treated carbon paper to fabricate an integrated three-dimensional electrode that affords a current density of 10 mA cm⁻² at a small overpotential of 182 mV and a low Tafel slope of 35 mV decade⁻¹ in basic media. The Faradaic efficiency of core-shell Ni_0.66Fe_0.17W_0.17S₂@amorphous NiFeW(OH)_z is as high as 99.5% for OER. The scanning electron microscope, transmission electron microscope, and X-ray photoelectron spectroscopy analyses confirm that this electrode has excellent stability in morphology and elementary composition after long-term electrochemical measurements. Importantly, density functional theory calculations further indicate that the core-shell heterojunction increased the conductivity of the catalyst, optimized the adsorption energy of the OER intermediates, and improved the OER activity. This study provides a universal strategy for designing more active core-shell structure electrocatalysts based on the rule of coordinated regulation between electronic transport and active sites.

Vanadium oxide cathode materials with stable crystal structure and fast Zn²⁺ storage capabilities are extremely important to achieving outstanding electrochemical performance in aqueous zinc-ion batteries. In this work, a one-step hydrothermal method was used to manipulate the bimetallic ion intercalation into the interlayer of vanadium oxide. The pre-intercalated Cu ions act as pillars to pin the vanadium oxide (V-O) layers, establishing stabilized two-dimensional channels for fast Zn²⁺ diffusion. The occupation of Mn ions between V-O interlayer further expands the layer spacing and increases the concentration of oxygen defects (O_d), which boosts the Zn²⁺ diffusion kinetics. As a result, as-prepared Cu_0.17Mn_0.03V₂O_5−□·2.16H₂O cathode shows outstanding Zn-storage capabilities under room- and low-temperature environments (e.g., 440.3 mAh g⁻¹ at room temperature and 294.3 mAh g⁻¹ at −60°C). Importantly, it shows a long cycling life and high capacity retention of 93.4% over 2500 cycles at 2 A g⁻¹ at −60°C. Furthermore, the reversible intercalation chemistry mechanisms during discharging/charging processes were revealed via operando X-ray powder diffraction and ex situ Raman characterizations. The strategy of a couple of 3d transition metal doping provides a solution for the development of superior room-/low-temperature vanadium-based cathode materials.