Search

The missions in extreme environments such as the moon, the Arctic/Antarctic, and the plateau require the operation of batteries at low temperatures even below the freezing point of water. Herein, it is reported that compressively stressed Co single atoms exhibit enhanced oxygen reduction reaction (ORR) activity and enable the effective operation of zinc–air battery at a subzero temperature. The compressive strain is generated by depositing Co single atoms on highly arced carbon layers with ultra‐small curvature radii ≈2 nm. The locally compressive strain on Co single atoms redistributes the electron fillings in d orbitals with different spatial orientations, thereby strengthening the adsorption of active intermediates and enhancing the activity toward ORR. As expected, compressively stressed Co single atoms outperform Co single atoms on a flat support without strain in terms of kinetic current density (31.09 mA cm−2 vs 0.35 mA cm−2) at 0.85 V during ORR. The integration of the catalyst into a Zn–air battery generates a superior power density of 54.8 mW cm−2 than the commercial Pt/C counterpart (24.1 mW cm−2) at −40 °C. [ABSTRACT FROM AUTHOR]

The successful separation of photoexcited charge carriers and their effective utilization are crucial for overcoming the slow kinetics of the four-electron process for photocatalytic oxygen evolution. Herein, a novel strategy utilizing urea as a source of N-doping on Ca _2 Nb _3 O _10 nanosheets is adopted, followed by the successful deposition of Co single atoms (Co-SAs) to achieve a synergistic effect. The presence of N-dopants and Co-SAs is validated via various experimental techniques. It is also observed that the presence of N-doping contributed towards the deposition of higher content of Co-SAs (0.21 wt%) in Ca _2 Nb _3 O _10− _x N _x -Co _SA nanosheets compared to 0.15 wt% for non-doped Ca _2 Nb _3 O _10 -Co _SA . The optimized Ca _2 Nb _3 O _10− _x N _x -Co _SA nanosheets exhibited an impressive photocatalytic O _2 evolution of ∼727.22 µ mol g ^−1 h ^−1 via the synergy of N-dopants and Co-SAs. As a result, the O _2 evolution response of Ca _2 Nb _3 O _10− _x N _x -Co _SA is 3.6 times higher than that of pristine Ca _2 Nb _3 O _10 nanosheets (201.26 µ mol g ^−1 h ^−1 ), 2.24 times better than Ca _2 Nb _3 O _10− _x N _x nanosheets (323.42 µ mol g ^−1 h ^−1 ), and 1.77 times higher compared to Ca _2 Nb _3 O _10 -Co _SA , (409.33 µ mol g ^−1 h ^−1 ), which clearly demonstrated the synergistic effect of N-dopants and Co-SAs in Ca _2 Nb _3 O _10− _x N _x -Co _SA nanosheets. Based on the findings of various characterization techniques, the co-presence of N-dopants and Co-SAs is observed to contribute towards better charge carrier separation, and utilization to achieve superior photocatalytic response. Thus, this study presents a novel approach for incorporating N-dopants and Co-SAs on Ca _2 Nb _3 O _10 nanosheets, which can be extended to a wide range of nanosheets produced by the soft chemical exfoliation method.

It is of great significance to synergistically modulate d -band centers (ε d) of multiple transition metals (TMs) for designing and developing highly efficient hybridized-electrocatalysts. Herein, the downshift in Co ε d is realized by synthesizing Co single atoms with low nitrogen-coordination number (CoN 2) at high T during the pyrolysis step while upshifting Ru ε d is achieved via decreasing Ru precursor mass to anchor Ru nanoclusters instead of nanoparticles on CoN 2 −containing carbon substrates (CoN 2 /Ru−NC). In our strategy, the downshift in Co ε d leads to a favorable affinity between Co sites of CoN 2 /Ru−NC and H* for desorption of H 2 ; additionally, upshifting Ru ε d helps the adsorption of OH* intermediates on Ru nanoclusters for CoN 2 /Ru−NC to promote water dissociation toward accelerating alkaline producing H 2. In consequence, CoN 2 /Ru−NC demonstrates an outstanding activity with an ultralow overpotential of ∼ 9.0 mV at 10.0 mA cm−2, which suppresses activities of Pt/C (24.0 mV) and most previously-reported Ru-based electrocatalysts. [Display omitted] • Our strategy anchors Ru nanoclusters on CoN 2 −containing carbon substrates. • Downshifting Co d -band center (ε d) activates Co atoms as catalytical sites. • Upshifting Ru ε d promotes H 2 O dissociation on Ru nanoclusters for alkaline HER. • This work provides a new way to design efficient electrocatalyst by modulating ε d. [ABSTRACT FROM AUTHOR]

Green fuel from water splitting is hardcore for future generations, and the limited source of fresh water (<1%) is a bottleneck. Seawater cannot be used directly as a feedstock in current electrolyzer techniques. Until now single atom catalysts were reported by many synthetic strategies using notorious chemicals and harsh conditions. A cobalt single-atom (CoSA) intruding cobalt oxide ultrasmall nanoparticle (Co 3 O 4 USNP)-intercalated porous carbon (PC) (CoSA-Co 3 O 4 @PC) electrocatalyst was synthesized from the waste orange peel as a single feedstock (solvent/template). The extended X-ray absorption fine structure spectroscopy (EXAFS) and theoretical fitting reveal a clear picture of the coordination environment of the CoSA sites (CoSA-Co 3 O 4 and CoSA-N 4 in PC). To impede the direct seawater corrosion and chlorine evolution the seawater has been desalinated (Dseawater) with minimal cost and the obtained PC is used as an adsorbent in this process. CoSA-Co 3 O 4 @PC shows high oxygen evolution reaction (OER) activity in transitional metal impurity-free (TMIF) 1 M KOH and alkaline Dseawater. CoSA-Co 3 O 4 @PC exhibits mass activity that is 15 times higher than the commercial RuO 2 . Theoretical interpretations suggest that the optimized CoSA sites in Co 3 O 4 USNPs reduce the energy barrier for alkaline water dissociation and simultaneously trigger an excellent OER followed by an adsorbate evolution mechanism (AEM)., (© 2023 Wiley-VCH GmbH.)

Lithium-sulfur (Li-S) battery possess the advantage of high specific energy but suffer from unstable cyclic performance due to the sluggish liquid-solid conversion kinetics causing severe lithium polysulfides (LiPS) shuttling. Designing multifunctional electrocatalysts with improved activity and abundant active sites to regulate the dynamics for sulfur electrochemistry is still a significant challenge. Herein, we proposed a thiourea assisted pyrolysis combined with hard template method to synthesize cobalt single atoms co-coordinated by N and S atoms embedded hollow carbon spheres (Co-NS-HCS) as a novel sulfur host. The Co-NS-HCS mainly consists of well-dispersed Co-N 3 S-C center sites where Co is co-bonded by N and S atoms. Systematical characterizations revealed that the Co-NS-HCS exhibit improved SRR electrocatalytic properties with higher exchange current density and larger electron transfer number than that of Co-N-HCS. When equipped in sulfur cathodes, the S@Co-NS-HCS exhibits superior rate performance (925 mAh g−1 at 2 C), long cycle stability (69.1% of capacity retention after 500 cycles at 1 C). Moreover, the assembled Li-S pouch type cell also exhibits competitive cyclic performance that work stably for 100 cycles at 0.1 C with a high capacity retention of 84.7%. This work furnishes a feasible scheme for the rational design of single atoms catalysts with improved electrocatalytic activity for sulfur cathodes based on the coordination environment regulation strategy. Cobalt single atoms co-coordinated by N and S atoms embedded hollow carbon spheres is synthesized as a highly efficient sulfur electrocatalyst to boost both the sulfur reduction and Li 2 S oxidation for advanced Li-S batteries with improved cyclic performance. [Display omitted] • Co single atoms coordinated by N/S are designed as efficient electrocatalysts. • The redox reaction kinetics of LiPS are boosted through S modulation. • The shuttle effect of LiPS is efficiently suppressed. • A high capacity retention of 84.7% is obtained in Li-S pouch cell. [ABSTRACT FROM AUTHOR]

MoS 2 represents a promising catalyst for the hydrogen evolution reaction (HER) in water splitting, but the inefficient catalytic activity in a pH-universal environment is an obstacle to developing practical applications. Boosting and balancing the water dissociation and hydrogen desorption kinetics is crucial in designing high-performance catalysts for the overall pH range. Herein, it is experimentally demonstrated that cobalt single-atom doping can effectively construct a reactive CoMoS micro-environment on the basal plane of MoS 2 and thus alter the uniformity of surface electron density, which is further confirmed by the theoretical results. The reactive micro-environment consisting of single-atom Co with the surrounding Mo and S atoms possesses excellent water dissociation and hydrogen desorption kinetics, exhibiting a superior performance of 36 mV at 10 mA cm -2 with a Tafel slope of 33 mV dec -1 in the alkaline condition. Meanwhile, it also shows worthy activity in the acidic (97 mV) and neutral (117 mV) environments. This work provides a facile strategy to improve the HER catalysis of MoS 2 in pH-universal environments., (© 2022 Wiley-VCH GmbH.)

[Display omitted] • A novel 3D monolithic MoS 2 /CoSAs-NS-CNTs@CoS 2 /CC electrode is fabricated via a pyrolysis−oxidation−sulfidation coupled strategy. • The 3D hierarchical structure with abundant open spaces and porosities largely increases the number of accessible active sites. • The MoS 2 /CoSAs-NS-CNTs@CoS 2 /CC electrode exhibits outstanding electrocatalytic HER performance in acidic and alkaline solutions. • The electron transfer along a pathway of CoS 2 →CoSAs-NS-CNTs→MoS 2 induces the electron accumulation on MoS 2 , thus boosting HER activity. • The possible HER activity enhancement mechanism of MoS 2 /CoSAs-NS-CNTs@CoS 2 /CC electrode is further clarified by DFT calculations. A multicomponent 3D monolithic electrode was designed that consists of Co single atoms anchored/nitrogen, sulfur co-doped carbon nanotubes (CoSAs-NS-CNTs) on carbon cloth (CC) with ultra-thin MoS 2 nanosheets externally decorated and ultra-small CoS 2 nanodots internally confined (MoS 2 /CoSAs-NS-CNTs@CoS 2 /CC) to form a hybrid heterojunction electrode with double interfaces as vectorial electron transport pathways for promoting electrocatalytic performance. The integration of well-distributed MoS 2 nanosheets and CoS 2 nanodots linked with Co single atoms anchored/N, S co-doped CNTs endows abundant multiple active sites, outstanding conductivity, and the downshifted d-band center with a thermodynamically favorable hydrogen adsorption free energy (ΔG H*) for effectively catalyzing hydrogen evolution reaction (HER). As a result, the optimal MoS 2 /CoSAs-NS-CNTs@CoS 2 /CC electrode exhibits outstanding HER performance with overpotentials of 72 and 56 mV at 10 mA cm−2 and small Tafel slopes of 59.4 and 43.2 mV dec-1 in acidic and alkaline solutions, respectively, outperforming most of the previously reported molybdenum/cobalt sulfide-based electrocatalysts. Moreover, the electrode also displays good durability and stability reflected from the small decrease on activity after 5000 CV cycles and nearly no decay in current density after electrolysis for 20 h. [ABSTRACT FROM AUTHOR]

Hitherto, developing an economical and stable high-activity bifunctional Pt catalyst for oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) becomes necessary for fuel cells and regeneration fuel cell system. However, how to uniformly disperse and firmly fix Pt nanoparticles (NPs) on carbon support with optimal particle size for catalysis is still a big challenge. Herein, by taking advantage of the isolating effect of the cobalt (Co) single atom site to Pt, strong interaction between Co single atoms and Pt, and the confinement of the porous carbon matrix derived metal organic frameworks, we successfully evenly immobilize Pt NPs on ZnCo-ZIF originated porous nitrogen-doped carbon matrix with rich cobalt single atoms (Co SAs-ZIF-NC) as multiple active sites. Compared with the commercial Pt/C catalyst, Pt@Co SAs-ZIF-NC, with ultralow Pt loading and ideal particle size, not only increases the active center, but also promotes the catalysis kinetics, greatly improving the ORR and HER catalytic activity. Under acidic conditions, its half-wave potential (0.917 V) is superior to commercial Pt/C (0.868 V), and the mass activity (0.48 A per mgPt) at 0.9 V is 3 times that of Pt/C (0.16 A per mgPt), surpassing the U.S. DOE target of 0.44 A per mgPt. Besides, it also shows outstanding HER performance. At 20 and 30 mV, its mass activity is even 4.5 and 13.6 times that of Pt/C. When further employed for HER in seawater, its mass activity is about 4 times as high as that of Pt/C, demonstrating the great potential applications. By using Co single atom sites in Co SAs-ZIF-NC to isolate Pt, the obtained Pt@Co SAs-ZIF-NC catalyst, with uniform and highly dispersed Pt nanoparticles on porous Co SAs-ZIF-NC, presents highly efficient and stable dual-function catalysis toward oxygen reduction and hydrogen evolution reactions. [Display omitted] • Single Co atom sites in Co SAs-ZIF-NC can isolate Pt and own strong interaction with Pt. • Obvious synergistic effect exists between Co single atom sites and Pt NPs in Pt@Co SAs-ZIF-NC catalysts. • With uniform and highly dispersed Pt NPs, Pt@Co SAs-ZIF-NC exhibits greatly enhanced ORR performance in acidic media. • In acidic media and seawater, high HER performance beyond commercial Pt catalysts is also obtained for the catalyst. • It provides a promising method for designing and constructing highly active and stable ultralow Pt-loaded catalysts. [ABSTRACT FROM AUTHOR]