Aqueous zinc metal batteries are appealing candidates for grid energy storage. However, the inadequate electrochemical reversibility of the zinc metal negative electrode inhibits the battery ...performance at the large-scale cell level. Here, we develop practical ampere-hour-scale aqueous Zn metal battery pouch cells by engineering the electrolyte solution. After identifying the proton reduction as the primary source of H
evolution during Zn metal electrodeposition, we design an electrolyte solution containing reverse micelle structures where sulfolane molecules constrain water in nanodomains to hinder proton reduction. Furthermore, we develop and validate an electrochemical testing protocol to comprehensively evaluate the cell's coulombic efficiency and zinc metal electrode cycle life. Finally, using the reverse micelle electrolyte, we assemble and test a practical ampere-hour Zn||Zn
V
O
•nH
O multi-layer pouch cell capable of delivering an initial energy density of 70 Wh L
(based on the volume of the cell components), capacity retention of about 80% after 390 cycles at 56 mA g
and ~25 °C and prolonged cycling for 5 months at 56 mA g
and ~25 °C.
Metallic phthalocyanines are promising electrocatalysts for CO2 reduction reaction (CO2RR). However, their catalytic activity and stability (especially under high potential) are still unsatisfactory. ...Herein, we synthesized a covalent organic polymer (COP‐CoPc) by introducing charge‐switchable viologen ligands into cobalt phthalocyanine (CoPc). The COP‐CoPc exhibits great activity for CO2RR, including a high Faradaic efficiency over a wide potential window and the highest CO partial current density among all ligand‐tuned phthalocyanine catalysts reported in the H‐type cell. Particularly, COP‐CoPc also shows great potential for practical applications, for example, a FECO of >95% is realized at a large current density of 150 mA/cm2 in a two‐electrode membrane electrode assembly reactor. Ex situ and in situ X‐ray absorption fine structure spectroscopy measurements and theory calculations reveal that when the charge‐switchable viologen ligands switch to neutral‐state ones, they can act as electron donors to enrich the electron density of Co centers in COP‐CoPc and enhance the desorption of *CO, thus improving the CO selectivity. Moreover, the excellent reversible redox capability of viologen ligands and the increased Co–N bonding strength in the Co–N4 sites enable COP‐CoPc to possess outstanding stability under elevated potentials and currents, enriching the knowledge of charge‐switchable ligands tailored CO2RR performance.
We synthesized a covalent organic polymer (COP‐CoPc) by introducing charge‐switchable viologen ligands into cobalt phthalocyanine (CoPc). When the charge‐switchable viologen ligands switch to a neutral state, they act as electron donors to enrich the electron density of Co centers in COP‐CoPc and enhance the desorption of *CO, thus increasing the CO selectivity. Moreover, the excellent reversible redox capability of viologen ligands and the strong Co–N bonding strength in the Co–N4 sites enable COP‐CoPc to possess outstanding stability under elevated potentials and currents.
Metallic phthalocyanines (MePcs) have shown their potential as catalysts for CO2 reduction reactions (CO2RR). However, their low conductivity, easy agglomeration, and poor stability enslave the ...further progress of their CO2RR applications. Herein, an integrated heterogeneous molecular catalyst through anchoring CoPc molecules on 3D nitrogen‐doped vertical graphene arrays (NVG) on carbon cloth (CC) is reported. The CoPc‐NVG/CC electrodes exhibit superior performance for reducing CO2 to CO with a Faradic efficiency of above 97.5% over a wide potential range (99% at an optimal potential), a very high turnover frequency of 35800 h−1, and decent stability. It is revealed that NVG interacts with CoPc to form highly efficient channels for electron transfer from NVG to CoPc, facilitating the Co(II)/Co(I) redox of CO2 reduction. The strong coupling effect between NVG and CoPc molecules not only endows CoPc with high intrinsic activity for CO2RR, but also enhances the stability of electrocatalysts under high potentials. This work paves an efficient approach for developing high‐performance heterogeneous catalysts by using rationally designed 3D integrated graphene arrays to host molecular metallic phthalocyanines so as to ameliorate their electronic structures and engineer stable active sites.
Three‐dimensional nitrogen‐doped vertical graphene arrays (NVG) are designed and utilized as scaffolds to anchor highly dispersed CoPc molecules to obtain an integrated heterogeneous molecular catalyst (CoPc‐NVG/CC). The strong coupling effect between NVG with CoPc not only endows CoPc with high intrinsic activity for CO2RR but also enhances the stability of electrocatalysts under high potentials.
Spinel cobalt oxides (Co3O4) have emerged as a promising class of catalysts for the electrochemical nitrate reduction reaction (eNO3RR) to ammonia, offering advantages such as low cost, high ...activity, and selectivity. However, the specific role of crystallographic facets in determining the catalysts’ performance remains elusive, impeding the development of efficient catalysts. In this study, we have synthesized various Co3O4 nanostructures with exposed facets of {100}, {111}, {110}, and {112}, aiming to investigate the dependence of the eNO3RR activity on the crystallographic facets. Among the catalysts tested, Co3O4 {111} shows the best performance, achieving an ammonia Faradaic efficiency of 99.1 ± 1.8% with a yield rate of 35.2 ± 0.6 mg h–1 cm–2 at −0.6 V vs RHE. Experimental and theoretical results reveal a transformation process in which the active phases evolve from Co3O4 to Co3O4–x with oxygen vacancy (Ov), followed by a Co3O4–x -Ov/Co(OH)2 hybrid, and finally Co(OH)2. This process is observed for all facets, but the formation of Ov and Co(OH)2 is the most rapid on the (111) surface. The presence of Ov significantly reduces the free energy of the *NH2 intermediate formation from 1.81 to −0.53 eV, and plentiful active sites on the densely reconstructed Co(OH)2 make Co3O4 {111} an ideal catalyst for ammonia synthesis via eNO3RR. This work provides insights into the understanding of the realistic active components, offers a strategy for developing highly efficient Co-based spinel catalysts for ammonia synthesis through tuning the exposed facets, and helps further advance the design and optimization of catalysts in the field of eNO3RR.
Li–S batteries present great potential to realize high-energy-density storage, but their practical implementation is severely hampered by the notorious polysulfide shuttling and the sluggish redox ...kinetics. While rationally designed redox mediators can optimize polysulfide conversion, the efficiency and stability of such a mediation process still remain formidable challenges. Herein, a strategy of constructing a “dual mediator system” is proposed for achieving efficient and durable modulation of polysulfide conversion kinetics by coupling well-selected solid and electrolyte-soluble mediators. Theoretical prediction and detailed electrochemical analysis reveal the structure–activity relationships of the two mediators in synergistically optimizing the redox conversions of sulfur species, thus achieving a deeper mechanistic understanding of a function-supporting mediator system design toward sulfur electrochemistry promotion. Specifically, such a dual mediator system realizes the bridging of full-range “electrochemical catalysis” and strengthened “chemical reduction” processes of sulfur species as well as greatly suppressed mediator deactivation/loss due to the beneficial interactions between each mediator component. Attributed to these advantageous features, the Li–S batteries enable a slow capacity decay of 0.026% per cycle over 1200 cycles and a desirable capacity of 8.8 mAh cm–2 with 8.2 mg cm–2 sulfur loading and lean electrolyte condition. This work not only proposes an effective mediator system design strategy for promoting Li–S battery performance but also inspires its potential utilization facing other analogous sophisticated electrochemical conversion processes.
High-efficiency hydrogen production using nonprecious electrocatalysts is considered a feasible solution for solving energy and environmental crises. Herein, we first develop a novel, simple, rapid, ...and environmentally friendly plasma-induced transformation approach to
in situ
engineer MOF-derived heterointerface catalyst. The plasma engineered MOF-derived Co
4
N-Co
3
O
4
-C has a well-defined interface structure and exhibits remarkable electrocatalytic performance for alkaline hydrogen evolution with a very low overpotential of 46 mV at 10 mA cm
−2
. Theory calculation verifies that the formation of heterointerface induces electron redistribution mainly in the interface region, particularly to the side of Co
4
N, triggering interface Co as active sites, in which there is stronger water capture capability, decreasing the energetic barrier of water dissociation, and optimal hydrogen absorption. This work presents a feasible and ingenious strategy to design and synthesize diverse electrocatalysts with MOF-derived heterointerface.
A novel, simple, and environmentally friendly plasma induced transformation approach to
in situ
engineer MOF-derived heterointerface catalyst is reported.
Development of high‐performance and low‐cost nonprecious metal electrocatalysts is critical for eco‐friendly hydrogen production through electrolysis. Herein, a novel nanoflower‐like electrocatalyst ...comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy directly on a porous nitrogen‐doped graphic carbon framework (denoted as Nix
Cuy
@ NG‐NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Nix
Cuy
@ NG‐NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni3Cu1@ NG‐NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 84.2 mV dec−1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm−2 with a low Tafel slope of 77.1 mV dec−1 in acidic electrolyte.
A novel nanoflower‐like electrocatalyst comprising few‐layer nitrogen‐doped graphene‐encapsulated nickel–copper alloy on a porous nitrogen‐doped graphic carbon framework is synthesized by a facile and scalable method, and exhibits high activity and excellent stability for hydrogen evolution due to the collective effects, including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and the graphene shell.
The electrocatalytic nitrogen reduction reaction (e-NRR), an eco-friendly and economical approach to convert nitrogen to ammonia under mild conditions, has received widespread attention in recent ...years. Defect engineering has been illustrated to be an effective strategy to improve the catalytic activity and selectivity of electrocatalysts
via
changing the electronic states as well as creating additional active sites for reduction reactions. Thus far, various approaches have been adopted to tune the physical and chemical properties of catalyst materials by means of inducing defects of different types and varying their concentrations or locations in host materials. In this review, the mechanisms and design principles of defective electrocatalysts for the NRR are introduced, and the refined synthesis and characterization techniques of defect engineering are systematically summarized. Based on the recent advances in defect engineering of electrocatalysts for the NRR, the roles of various defect states, such as vacancies and the amorphous phase, in the catalytic enhancement mechanism are comprehensively discussed. Finally, perspectives on the challenges and opportunities in developing new cost-effective and high-efficiency NRR catalysts for practical applications are outlined.
Defect engineering of nanostructured electrocatalysts for enhancing the nitrogen reduction reaction is systematically reviewed with challenges and opportunities for further research discussed.
