Insight into the bubble-induced overpotential towards high-rate charging of Zn-air batteries

The rational design of bifunctional catalysts with excellent activity and stability toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for rechargeable Zn‐air batteries (ZABs). In this study, a facile coordination bridging strategy is proposed to construct bifunctional Co‐CoN4 hybrid active sites embedded in porous N‐rich carbon nanolamellas (denoted as Co‐CoN4@NCNs) for both the ORR and OER. Synchrotron X‐ray absorption spectroscopy and density functional theory calculations reveal that the increased intrinsic ORR/OER activities can be attributed to the efficient interfacial charge transfer between the atomic CoN sites and metallic Co sites due to their robust electronic correlation. In situ Raman spectroscopy confirms that the OER activity depends on the CoOOH intermediates formed during the reaction. Co‐CoN4@NCNs exhibits superior bifunctional catalytic performance for the ORR (E1/2 = 0.83 V) and OER (η = 310 mV at 10 mA cm−2) conducted in alkaline media. The assembled rechargeable Co‐CoN4@NCNs‐based ZAB displays an open‐circuit voltage of 1.47 V, peak power density of 118.8 mW cm−2, specific capacity of 776.7 mAh g−1, and outstanding cycling stability over 1500 cycles. The regulation of the interfacial electronic properties can contribute to the rational design of bifunctional electrocatalysts used in rechargeable metal‐air batteries.

Robust Electronic Correlation of Co‐CoN4 Hybrid Active Sites for Durable Rechargeable Zn‐Air Batteries

Oxygen and sulfur dual vacancies engineering on 3D Co3O4/Co3S4 heterostructure to improve overall water splitting activity

The design and construction of electrocatalysts with high efficiency, low cost and large current output suitable for industrial hydrogen production is the current development trend for water electrolysis. Herein, a lattice‐confined in situ reduction effect of the 3D crystalline fullerene network (CFN) is developed to trap Ru nanoparticle (NP) and single atom (SA) via a solvothermal‐pyrolysis process. The optimized product (RuNP‐RuSA@CFN‐800) exhibits outstanding electrocatalytic performance for alkaline hydrogen evolution reactions. To deliver a current density of 10 mA cm−2, the RuNP‐RuSA@CFN‐800 merely required an overpotential of 33 mV, along with a robust electrocatalytic durability for 1400 h. Even at large current densities of 500 and 1000 mA cm−2, the overpotentials are only 154 and 251 mV, respectively. Density function theorey calculation results indicated that the electronic synergetic effect between Ru NP and SA enable to regulate the charge distribution of RuNP‐RuSA@CFN‐800 and reduce the Gibbs free energy of intermediate species for water dissociation process, thereby accelerating the hydrogen evolution process. Moreover, the robust CFN matrix render this strategy patulous to other transition metals, e.g., Cu, Ni, and Co. The present study provides a new clue for the construction of novel electrocatalyst in the field of energy storage and conversion.

Fullerene Lattice‐Confined Ru Nanoparticles and Single Atoms Synergistically Boost Electrocatalytic Hydrogen Evolution Reaction

Abstract Rechargeable zinc-air batteries (ZABs) are a promising energy conversion device, which rely critically on electrocatalysts to accelerate their rate-determining reactions such as oxygen reduction (ORR) and oxygen evolution reactions (OER). Herein, we fabricate a range of bifunctional M–N–C (metal-nitrogen-carbon) catalysts containing M–N x coordination sites and M/M x C nanoparticles (M = Co, Fe, and Cu) using a new class of γ-cyclodextrin (CD) based metal–organic framework as the precursor. With the two types of active sites interacting with each other in the catalysts, the obtained Fe@C-FeNC and Co@C-CoNC display superior alkaline ORR activity in terms of low half-wave ( E 1/2 ) potential (~ 0.917 and 0.906 V, respectively), which are higher than Cu@C-CuNC (~ 0.829 V) and the commercial Pt/C (~ 0.861 V). As a bifunctional electrocatalyst, the Co@C-CoNC exhibits the best performance, showing a bifunctional ORR/OER overpotential (Δ E ) of ~ 0.732 V, which is much lower than that of Fe@C-FeNC (~ 0.831 V) and Cu@C-CuNC (~ 1.411 V), as well as most of the robust bifunctional electrocatalysts reported to date. Synchrotron X-ray absorption spectroscopy and density functional theory simulations reveal that the strong electronic correlation between metallic Co nanoparticles and the atomic Co-N 4 sites in the Co@C-CoNC catalyst can increase the d-electron density near the Fermi level and thus effectively optimize the adsorption/desorption of intermediates in ORR/OER, resulting in an enhanced bifunctional electrocatalytic performance. The Co@C-CoNC-based rechargeable ZAB exhibited a maximum power density of 162.80 mW cm −2 at 270.30 mA cm −2 , higher than the combination of commercial Pt/C + RuO 2 (~ 158.90 mW cm −2 at 265.80 mA cm −2 ) catalysts. During the galvanostatic discharge at 10 mA cm −2 , the ZAB delivered an almost stable discharge voltage of 1.2 V for ~ 140 h, signifying the virtue of excellent bifunctional ORR/OER electrocatalytic activity. 

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Mutual Self-Regulation of d-Electrons of Single Atoms and Adjacent Nanoparticles for Bifunctional Oxygen Electrocatalysis and Rechargeable Zinc-Air Batteries

The development of low‐cost multifunctional electrocatalysts with high activity for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) is critical for the advancement of sophisticated energy conversion and storage devices. Herein, a trifunctional Ni(S0.51Se0.49)2@NC catalyst is designed and fabricated using a dianionic regulation strategy. Synchrotron radiation X‐ray absorption spectroscopy and density functional theory calculations reveal that simultaneous sulfidation and selenization can induce the electronic delocalization of Ni(S0.51Se0.49)2 active sites to enhance the adsorption of *OOH/*OH intermediate for ORR/OER and H* intermediate for HER. The OER and HER mechanisms are revealed by in situ Raman spectroscopy. The Ni(S0.51Se0.49)2@NC exhibits trifunctional catalytic activity for the HER (111 mV at 10 mA cm−2), OER (320 mV at 10 mA cm−2), and ORR (half‐wave potential of 0.83 V). The rechargeable zinc–air batteries (ZABs) exhibit an open‐circuit voltage of 1.46 V, a specific capacity of 799.1 mAh g−1, and excellent stability for 1000 cycles. The water electrolytic cell using Ni(S0.51Se0.49)2@NC electrodes delivers a current density of 10 mA cm−2 at a cell voltage of 1.59 V, and it can be powered using the constructed ZABs. These findings contribute to developing low‐cost and efficient non‐noble metal multifunctional catalysts.

Dianion Induced Electron Delocalization of Trifunctional Electrocatalysts for Rechargeable Zn–Air Batteries and Self‐Powered Water Splitting

Objectives The influence of commercial helium–oxygen saturation diving on divers’ gut microbiotas was assessed to provide dietary suggestion. Methods Faecal samples of 47 divers working offshore were collected before (T1), during (T2) and after (T3) saturation diving. Their living and excursion depths were 55–134 metres underwater with a saturation duration of 12–31 days and PaO2 of 38–65 kPa. The faecal samples were examined through 16S ribosomal DNA amplicon sequencing based on the Illumina sequencing platform to analyse changes in the bacteria composition in the divers’ guts. Results Although the α and β diversity of the gut microbiota did not change significantly, we found that living in a hyperbaric environment of helium–oxygen saturation decreased the abundance of the genus Bifidobacterium, an obligate anaerobe, from 2.43%±3.83% at T1 to 0.79%±1.23% at T2 and 0.59%±0.79% at T3. Additionally, the abundance of some short-chain fatty acid (SCFA)-producing bacteria, such as Fusicatenibacter, Faecalibacterium, rectale group and Anaerostipes, showed a decreased trend in the order of before, during and after diving. On the contrary, the abundance of species, such as Lactococcus garvieae, Actinomyces odontolyticus, Peptoclostridium difficile, Butyricimonas virosa, Streptococcus mutans, Porphyromonas asaccharolytica and A. graevenitzii, showed an increasing trend, but most of them were pathogens. Conclusions Occupational exposure to high pressure in a helium–oxygen saturation environment decreased the abundance of Bifidobacterium and some SCFA-producing bacteria, and increased the risk of pathogenic bacterial infection. Supplementation of the diver diet with probiotics or prebiotics during saturation diving might prevent these undesirable changes.

Changes in the gut microbiota during and after commercial helium-oxygen saturation diving in China

Efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for rechargeable Zn-air batteries (ZABs). Herein, an oxygen-respirable sponge-like Co@C-O-Cs catalyst with oxygen-rich active sites was designed and constructed for both ORR and OER by a facile carbon dot-assisted strategy. The aerophilic triphase interface of Co@C-O-Cs cathode efficiently boosts oxygen diffusion and transfer. The theoretical calculations and experimental studies revealed that the Co-C-COC active sites can redistribute the local charge density and lower the reaction energy barrier. The Co@C-O-Cs catalyst displays superior bifunctional catalytic activities with a half-wave potential of 0.82 V for ORR and an ultralow overpotential of 294 mV at 10 mA cm-2 for OER. Moreover, it can drive the liquid ZABs with high peak power density (106.4 mW cm-2), specific capacity (720.7 mAh g-1), outstanding long-term cycle stability (over 750 cycles at 10 mA cm-2), and exhibits excellent feasibility in flexible all-solid-state ZABs. These findings provide new insights into the rational design of efficient bifunctional oxygen catalysts in rechargeable metal-air batteries. 

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Wei Jin

Papers

Dianion Induced Electron Delocalization of Trifunctional Electrocatalysts for Rechargeable Zn–Air Batteries and Self‐Powered Water Splitting

Robust Electronic Correlation of Co‐CoN4 Hybrid Active Sites for Durable Rechargeable Zn‐Air Batteries

Changes in the gut microbiota during and after commercial helium-oxygen saturation diving in China

Aerophilic Triphase Interface Tuned by Carbon Dots Driving Durable and Flexible Rechargeable Zn-Air Batteries

Sustainable recovery of lithium from spent LiFePO4 via proton circulation