Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary ...alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h
mg
(0.46 mmol h
cm
). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N
due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.
Abstract
Oxygen reduction reaction towards hydrogen peroxide (H
2
O
2
) provides a green alternative route for H
2
O
2
production, but it lacks efficient catalysts to achieve high selectivity and ...activity simultaneously under industrial-relevant production rates. Here we report a boron-doped carbon (B-C) catalyst which can overcome this activity-selectivity dilemma. Compared to the state-of-the-art oxidized carbon catalyst, B-C catalyst presents enhanced activity (saving more than 210 mV overpotential) under industrial-relevant currents (up to 300 mA cm
−2
) while maintaining high H
2
O
2
selectivity (85–90%). Density-functional theory calculations reveal that the boron dopant site is responsible for high H
2
O
2
activity and selectivity due to low thermodynamic and kinetic barriers. Employed in our porous solid electrolyte reactor, the B-C catalyst demonstrates a direct and continuous generation of pure H
2
O
2
solutions with high selectivity (up to 95%) and high H
2
O
2
partial currents (up to ~400 mA cm
−2
), illustrating the catalyst’s great potential for practical applications in the future.
Transition-metal single-atom catalysts present extraordinary activity per metal atomic site, but suffer from low metal-atom densities (typically less than 5 wt% or 1 at.%), which limits their overall ...catalytic performance. Here we report a general method for the synthesis of single-atom catalysts with high transition-metal-atom loadings of up to 40 wt% or 3.8 at.%, representing several-fold improvements compared to benchmarks in the literature. Graphene quantum dots, later interweaved into a carbon matrix, were used as a support, providing numerous anchoring sites and thus facilitating the generation of high densities of transition-metal atoms with sufficient spacing between the metal atoms to avoid aggregation. A significant increase in activity in electrochemical CO2 reduction (used as a representative reaction) was demonstrated on a Ni single-atom catalyst with increased Ni loading.Transition-metal single-atom catalysts display excellent activity per metal atom site, but suffer from low metal atom densities (typically less than 5 wt% or 1 at.%), which limits their overall catalytic performance. Now, the use of a graphene-quantum-dot primary support, later interweaved into a carbon matrix, has enabled the synthesis of single-atom catalysts with high transition-metal atom loadings of up to 40 wt% or 3.84 at.%.
While Ni‐rich cathode materials combined with highly conductive and mechanically sinterable sulfide solid electrolytes are imperative for practical all‐solid‐state Li batteries (ASLBs), they suffer ...from poor performance. Moreover, the prevailing wisdom regarding the use of LiNi,Co,MnO2 in conventional liquid electrolyte cells, that is, increased capacity upon increased Ni content, at the expense of degraded cycling stability, has not been applied in ASLBs. In this work, the effect of overlooked but dominant electrochemo‐mechanical on the performance of Ni‐rich cathodes in ASLBs are elucidated by complementary analysis. While conventional LiNi0.80Co0.16Al0.04O2 (NCA80) with randomly oriented grains is prone to severe particle disintegration even at the initial cycle, the radially oriented rod‐shaped grains in full‐concentration gradient LiNi0.75Co0.10Mn0.15O2 (FCG75) accommodate volume changes, maintaining mechanical integrity. This accounts for their different performance in terms of reversible capacity (156 vs 196 mA h g−1), initial Coulombic efficiency (71.2 vs 84.9%), and capacity retention (46.9 vs 79.1% after 200 cycles) at 30 °C. The superior interfacial stability for FCG75/Li6PS5Cl to for NCA80/Li6PS5Cl is also probed. Finally, the reversible operation of FCG75/Li ASLBs is demonstrated. The excellent performance of FCG75 ranks at the highest level in the ASLB field.
Unprecedentedly high electrochemical performance of Ni‐rich cathodes for all‐solid‐state Li batteries operating at room temperature is achieved and its origin is elucidated. While conventional LiNi0.80Co0.16Al0.04O2 with randomly oriented grains is prone to severe particle disintegration even at the initial cycle, the radially oriented rod‐shaped grains in full‐concentration gradient LiNi0.75Co0.10Mn0.15O2 accommodate volume changes, maintaining mechanical integrity.
Owing to their potential for greater safety, higher energy density, and scalable fabrication, bulk-type all-solid-state lithium-ion batteries (ASLBs) employing deformable sulfide superionic ...conductors are considered highly promising for applications in battery electric vehicles. While fabrication of sheet-type electrodes is imperative from the practical point of view, reports on relevant research are scarce. This might be attributable to issues that complicate the slurry-based fabrication process and/or issues with ionic contacts and percolation. In this work, we systematically investigate the electrochemical performance of conventional dry-mixed electrodes and wet-slurry fabricated electrodes for ASLBs, by varying the different fractions of solid electrolytes and the mass loading. This information calls for a need to develop well-designed electrodes with better ionic contacts and to improve the ionic conductivity of solid electrolytes. As a scalable proof-of-concept to achieve better ionic contacts, a premixing process for active materials and solid electrolytes is demonstrated to significantly improve electrochemical performance. Pouch-type 80 × 60 mm2 all-solid-state LiNi0·6Co0·2Mn0·2O2/graphite full-cells fabricated by the slurry process show high cell-based energy density (184 W h kg−1 and 432 W h L−1). For the first time, their excellent safety is also demonstrated by simple tests (cutting with scissors and heating at 110 °C).
Display omitted
•Slurry-mixed electrodes using polymeric binders suffer from poor ionic contacts.•Premixing of active materials and SEs significantly increases the capacity.•Pouch-type ASLBs with high energy density (184 W h kgcell−1) are fabricated.•Excellent safety for pouch-type ASLBs is demonstrated by cutting and heating tests.
For mass production of all‐solid‐state lithium‐ion batteries (ASLBs) employing highly Li+ conductive and mechanically sinterable sulfide solid electrolytes (SEs), the wet‐slurry process is ...imperative. Unfortunately, the poor chemical stability of sulfide SEs severely restrict available candidates for solvents and in turn polymeric binders. Moreover, the binders interrupt Li+‐ionic contacts at interfaces, resulting in the below par electrochemical performance. In this work, a new scalable slurry fabrication protocol for sheet‐type ASLB electrodes made of Li+‐conductive polymeric binders is reported. The use of intermediate‐polarity solvent (e.g., dibromomethane) for the slurry allows for accommodating Li6PS5Cl and solvate‐ionic‐liquid‐based polymeric binders (NBR‐Li(G3)TFSI, NBR: nitrile−butadiene rubber, G3: triethylene glycol dimethyl ether, LiTFSI: lithium bis(trifluoromethanesulfonyl)imide) together without suffering from undesirable side reactions or phase separation. The LiNi0.6Co0.2Mn0.2O2 and Li4Ti5O12 electrodes employing NBR‐Li(G3)TFSI show high capacities of 174 and 160 mA h g−1 at 30 °C, respectively, which are far superior to those using conventional NBR (144 and 76 mA h g−1). Moreover, high areal capacity of 7.4 mA h cm−2 is highlighted for the LiNi0.7Co0.15Mn0.15O2 electrodes with ultrahigh mass loading of 45 mg cm−2. The facilitated Li+‐ionic contacts at interfaces paved by NBR‐Li(G3)TFSI are evidenced by the complementary analysis from electrochemical and 7Li nuclear magnetic resonance measurements.
A new slurry‐fabricable solvate ionic liquid (SIL)‐based Li+‐conductive polymeric binder for all‐solid‐state lithium‐ion batteries is developed. Sheet‐type electrodes are tailored from a slurry using solvent with intermediate polarity (e.g., dibromomethane) which enables the accommodation of sulfide solid electrolytes and SIL together without suffering from any side reactions or phase separation. The resulting electrodes significantly outperform those made of conventional insulating binders.
Owing to the ever‐increasing safety concerns about conventional lithium‐ion batteries, whose applications have expanded to include electric vehicles and grid‐scale energy storage, batteries with ...solidified electrolytes that utilize nonflammable inorganic materials are attracting considerable attention. In particular, owing to their superionic conductivities (as high as ≈10−2 S cm−1) and deformability, sulfide materials as the solid electrolytes (SEs) are considered the enabling material for high‐energy bulk‐type all‐solid‐state batteries. Herein the authors provide a brief review on recent progress in sulfide Li‐ and Na‐ion SEs for all‐solid‐state batteries. After the basic principles in designing SEs are considered, the experimental exploration of multicomponent systems and ab initio calculations that accelerate the search for stronger candidates are discussed. Next, other issues and challenges that are critical for practical applications, such as instability in air, electrochemical stability, and compatibility with active materials, are discussed. Then, an emerging progress in liquid‐phase synthesis and solution process of SEs and its relevant prospects in ensuring intimate ionic contacts and fabricating sheet‐type electrodes is highlighted. Finally, an outlook on the future research directions for all‐solid‐state batteries employing sulfide superionic conductors is provided.
Sulfide Li+ and Na+ superionic conductors are considered to be enabling materials in safe and high‐energy all‐solid‐state batteries. This progress report provides a brief review on superionic conductor solid electrolytes through both experimental and theoretical approaches on ionic conductivity, electrochemical stability, interface compatibility, and air‐stability. Further, design strategies, practical considerations, and emerging solution processes of solid electrolytes are discussed.
All-solid-state lithium-ion batteries (ASLBs) employing sulfide solid electrolytes (SEs) have emerged as promising next-generation batteries for large-scale energy storage applications in terms of ...safety and high energy density. While slurry-based fabrication processes using polymeric binders and solvents are inevitable to produce sheet-type electrodes, these processes for ASLBs have been overlooked until now. In this work, we report the first scalable single-step fabrication of bendable sheet-type composite electrodes for ASLBs using a one-pot slurry prepared from SE precursors (Li 2 S and P 2 S 5 ), active materials (LiNi 0.6 Co 0.2 Mn 0.2 O 2 or graphite), and polymeric binders (nitrile-butadiene rubber (NBR) or polyvinyl chloride (PVC)) via a wet-chemical route using tetrahydrofuran. At 30 °C, the LiNi 0.6 Co 0.2 Mn 0.2 O 2 and graphite electrodes wet-tailored from SE precursors and NBR exhibit high capacities of 140 mA h g −1 at 0.1C and 320 mA h g −1 at 0.2C, respectively. Particularly, the rate capability of the graphite electrode in an all-solid-state cell is superior to that of a liquid electrolyte-based cell. Additionally, the effects of the size of the SE precursors and the polymeric binders on the electrochemical performance are investigated. Finally, the excellent electrochemical performance of LiNi 0.6 Co 0.2 Mn 0.2 O 2 /graphite ASLBs assembled using the as-single-step-fabricated electrodes are also demonstrated not only at 30 °C but also at 100 °C.
Electrochemical carbon-capture technologies, with renewable electricity as the energy input, are promising for carbon management but still suffer from low capture rates, oxygen sensitivity or system ...complexity
. Here we demonstrate a continuous electrochemical carbon-capture design by coupling oxygen/water (O
/H
O) redox couple with a modular solid-electrolyte reactor
. By performing oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) redox electrolysis, our device can efficiently absorb dilute carbon dioxide (CO
) molecules at the high-alkaline cathode-membrane interface to form carbonate ions, followed by a neutralization process through the proton flux from the anode to continuously output a high-purity (>99%) CO
stream from the middle solid-electrolyte layer. No chemical inputs were needed nor side products generated during the whole carbon absorption/release process. High carbon-capture rates (440 mA cm
, 0.137 mmol
min
cm
or 86.7 kg
day
m
), high Faradaic efficiencies (>90% based on carbonate), high carbon-removal efficiency (>98%) in simulated flue gas and low energy consumption (starting from about 150 kJ per mol
) were demonstrated in our carbon-capture solid-electrolyte reactor, suggesting promising practical applications.
The technical advancements made in DNA profiling now allow for very low DNA amounts to be analyzed. Accordingly, the argument often made in criminal courts is not who the DNA belongs to but rather ...how it was deposited. Despite the complexity of the relevant DNA transfer, persistence, prevalence, and recovery issues, forensic laboratories in some European countries have used evaluative reports with activity level propositions, while this is not current practice in the United States. The purpose of this study was to gain an overview of the opinions about activity level reporting (ALR) held by forensic biologists in the United States. A seventeen‐question survey was distributed to members of the American Society of Crime Laboratory Directors and U.S. members of the International Society for Forensic Genetics. The survey included multiple‐choice and open‐response questions and received 54 responses. The majority of responses expressed moderate support of ALR. Participants mentioned six major concerns to be addressed prior to implementing ALR in the United States: (1) effect of number of variables involved; (2) need of education for practitioners/legal system; (3) inadequate number of activity studies with realistic scenarios; (4) difficulty of achieving admissibility in court; (5) need for standardized approaches/guidelines; and (6) requisite shift in perspective as to the validity of ALR. Overall, this small segment of U.S. forensic DNA practitioners appear to be willing to implement ALR once these concerns are fully addressed and resolved. As a follow‐up, it would be worthwhile exploring these and other questions with a larger group and also other disciplines.
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