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Herein, Co/CoO heterojunction nanoparticles (NPs) rich in oxygen vacancies embedded in mesoporous walls of nitrogen‐doped hollow carbon nanoboxes coupled with nitrogen‐doped carbon nanotubes (P–Co/CoOV@NHCNB@NCNT) are well designed through zeolite‐imidazole framework (ZIF‐67) carbonization, chemical vapor deposition, and O2 plasma treatment. As a result, the three‐dimensional NHCNBs coupled with NCNTs and unique heterojunction with rich oxygen vacancies reduce the charge transport resistance and accelerate the catalytic reaction rate of the P–Co/CoOV@NHCNB@NCNT, and they display exceedingly good electrocatalytic performance for oxygen reduction reaction (ORR, halfwave potential [EORR, 1/2 = 0.855 V vs. reversible hydrogen electrode]) and oxygen evolution reaction (OER, overpotential (ηOER, 10 = 377 mV@10 mA cm−2), which exceeds that of the commercial Pt/C + RuO2 and most of the formerly reported electrocatalysts. Impressively, both the aqueous and flexible foldable all‐solid‐state rechargeable zinc–air batteries (ZABs) assembled with the P–Co/CoOV@NHCNB@NCNT catalyst reveal a large maximum power density and outstanding long‐term cycling stability. First‐principles density functional theory calculations show that the formation of heterojunctions and oxygen vacancies enhances conductivity, reduces reaction energy barriers, and accelerates reaction kinetics rates. This work opens up a new avenue for the facile construction of highly active, structurally stable, and cost‐effective bifunctional catalysts for ZABs. [ABSTRACT FROM AUTHOR]

Core–shell Fe3O4@CoO NCs have been demonstrated to be efficient bifunctional catalysts for the oxygen reduction (ORR) and evolution (OER) reactions. Their activities are strongly shell thickness dependent. Specifically, nanocrystals with ∼2 monolayers of CoO can exhibit a potential difference of 0.794 V at OER and ORR current densities of 10 and −3 mA cm−2, respectively. This value is competitive to those of most active bifunctional catalysts reported. In addition, they are also used as the oxygen cathode for Zn–air batteries and can deliver a peak power density of 109 mW cm−2, much higher than that of the Pt–RuO2/C (88.1 mW cm−2). [ABSTRACT FROM AUTHOR]

Keywords: acidic oxygen evolution reaction; defect engineering; nitrogen-doped carbon; oxygen-vacancy rich RuO2; super-high durability EN acidic oxygen evolution reaction defect engineering nitrogen-doped carbon oxygen-vacancy rich RuO2 super-high durability 1 1 1 06/20/23 20230616 NES 230616 B Acidic OER Catalysts b In article number 2300152, Zhong-Jie Jiang and co-workers use a strategy of ultrathin carbon coating and oxygen-vacancy generation to improve the activity and stability of the RuO SB 2 sb nano-catalysts towards the acidic oxygen evolution reaction. Acidic oxygen evolution reaction, defect engineering, nitrogen-doped carbon, oxygen-vacancy rich RuO2, super-high durability Ultrathin Carbon Coating and Defect Engineering Promote RuO2 as an Efficient Catalyst for Acidic Oxygen Evolution Reaction with Super-High Durability (Adv. [Extracted from the article]

Abstract: Nitrogen doped holey graphene (NHG), with in-plane holes in its sheet plate, has been synthesized in this work through the potassium hydroxide (KOH) etching and ball milling of nitrogen doped graphene (NG). It shows that the KOH etching and ball milling does not distinctly alter the elemental composition and the relative percentages of functional groups in NG, but produce holes in its in-plane sheet plate. The obtained NHG can then be used as an active electrode material for supercapacitors and as an active electrocatalyst for oxygen reduction reaction, and exhibits significantly higher electrochemical performance than the corresponding NG. Its improved electrochemical performance could be attributed to its specific holey structure in the sheet plate and porous structure in its randomly stacked solid, which provide it with more active edge atoms, better accessibility to electrolyte, larger accommodation space for ions, faster electrolyte diffusion and movement and so on. [Copyright &y& Elsevier]

In this work, plasma under different atmospheres is used to adjust the surface electronic and chemical structure of Fe/Co/N co-decorated hollow graphene spheres (FCNHGS) in order to create suitable conditions for the deposition of Pt 1 Ni 2 alloy nanoparticles (NPs). The results show that plasma treatment in specific atmospheres has different effects on the surface of FCNHGS, such as O 2 plasma is etching and oxidation, N 2 plasma and Ar plasma is etching, Ar/H 2 plasma is etching and reduction, Ar/NH 3 plasma is etching, doping and reduction. Therefore, changing the plasma treatment atmosphere can control the anchoring sites on FCNHGS for the deposition of Pt 1 Ni 2 NPs. When Ar/NH 3 plasma is used, the synthesized Pt 1 Ni 2 @Ar/NH 3 -FCNHGS exhibits the best bi-functional catalytic activity and the highest utilization efficiency of Pt in the oxygen reduction and hydrogen evolution reaction (ORR/HER) due to the strong interaction between loaded Pt 1 Ni 2 NPs and the Ar/NH 3 -FCNHGS. Moreover, when the Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is used as cathode catalyst for direct methanol fuel cell, it exhibits superior open-circuit voltage (OCV = 730 mV) and similar peak power density (PPD = 62.8 mW cm−2) to 20 wt% Pt/C from 25 to 80 °C. More importantly, it showed better stability compared with 20 wt% Pt/C after about 72 h of stability testing. [Display omitted] • The well-dispersed Pt 1 Ni 2 NPs on FCNHGS was achieved by plasma with different atmospheres. • The plasma with different atmospheres produced different defect levels on FCNHGS. • The NPs size is related to the strength of the interaction between the substrate and the alloy NPs. • The OES deduce the formation of defects/functional groups on substrate materials. • The Pt 1 Ni 2 @Ar/NH 3 -FCNHGS is demonstrated to be a stable and efficient catalyst for ORR/HER. [ABSTRACT FROM AUTHOR]

Noble metal Pt is the acknowledged efficient catalyst for oxygen reduction (ORR) and hydrogen evolution reaction (HER) in commercial applications. However, due to its high price and limited reserves, its large-scale application is limited. In order to overcome this defect, the loaded Pt nanoparticles (NPs) should be small and dispersed efficiently through the design of electrode materials, so as to improve the utilization efficiency of Pt. In addition, the introduction of non-noble metal active sites can reduce the consumption of Pt efficiently. In this work, hollow graphene spheres are used as the carrier and the heteroatoms (N, Fe and Co) are introduced. The results show that the introduction of Fe and Co can form very effective heteroatom active sites (carbon encapsulated Fe/Co metals and FeCo alloy, and/or metal nitrides Fe/Co-N x -C) in the substrate material, which improve the catalytic activity of the electrode material effectively and the utilization efficiency of Pt. In addition, the generation of Fe/Co-N x -C active sites and the loading of Pt are also closely related to the doped N atoms. The onset potential, limiting current density (J L), half-wave potential (E 1/2) and Tafel slope of sample FeCo-N x HGSs/Pt (10 wt%) can exceed or comparable to those of commercial catalysts Pt/C (20 wt%) towards ORR both in acid and alkaline electrolyte. Moreover, the values of η 100 and the Tafel slope for FeCo-N x HGSs/Pt towards HER can also exceed the commercial catalysts Pt/C (20 wt%) in acid and alkaline electrolytes. The purpose of reducing the usage amount of precious metals without reducing the catalytic performance is realized. The relationship between the ORR and HER performance of the resultant electrode catalyst and the doped heteroatoms, such as nitrogen (N), iron (Fe) and cobalt (Co) atoms, was studied and discussed in detail. [Display omitted] • Pyridine and pyrrole N are easy to the formation of metal nitrides (Fe(Co)-N x -C). • Pyridine N is closely related to the rivet of precious metal Pt. • The Fe/Co in HGSs exist in the form of Fe/Co metals, FeCo alloy, Fe/Co-N x -C. • The Fe/Co atoms play a positive role in improving the ORR and HER performance. • The FeCo-N x HGSs/Pt is a stable and efficient catalyst for ORR/HER. [ABSTRACT FROM AUTHOR]

Herein, ultra-low amount Pt is uniformly deposited on the surface of CoFe nanoparticles (NPs) embedded nitrogen-doped carbon nanotubes which are grown directionally on the surface of carbon fiber cloth (Pt–CoFe@NCNT/CFC) using the direct current plasma magnetron sputtering (DC-PMS) technique. The designed electrode exhibits excellent trifunctional catalytic activities towards oxygen reduction reaction (ORR) (in 0.1 M KOH, E 1/2 = 0.807 V; in 0.5 M H 2 SO 4 , E 1/2 = 0.723 V), hydrogen evolution reaction (HER) (in 1 M KOH, η 10 = 17 mV and η 100 = 93 mV; in 0.5 M H 2 SO 4 , η 10 = 42 mV and η 100 = 100.5 mV) and methanol oxidation reaction (MOR) (in 0.5 M H 2 SO 4 + 0.5 M CH 3 OH, peak current density reaches 115 mA mg−1 Pt @1.116 V). It is verified that the DC-PMS technique can greatly improve the utilization efficiency of Pt, so as to reduce the dosage of Pt, and shows better catalytic performance and excellent stability than the commercial Pt/C catalysts. The rich hierarchical heterostructures of the designed electrode can provide more non-noble metal active sites, so as to enhance the catalytic activity and further cut down the consumption of noble metals. Impressively, Pt–CoFe@NCNT/CFC electrode assembled direct methanol fuel cell achieved a remarkable maximum power density of 73.41 mW cm−2 and shows excellent stability. Pt nanoclusters are deposited on the surface of CoFe metal embedded nitrogen-doped carbon nanotubes by DC plasma magnetron sputtering technology, and the designed electrode exhibits excellent trifunctional catalytic activities towards ORR/MOR/HER. [Display omitted] • Pt is uniformly deposited on the surface of CoFe@NCNT/CFC using DC-PMS technique. • Abundant non-noble metal active sites are beneficial to reduce the consumption of Pt. • It provides abundant rivet points for the efficient deposition of Pt. • It shows stable and efficient ORR/MOR/HER multi-functional catalytic performance. • The assembled DMFC exhibits good performance and excellent stability. [ABSTRACT FROM AUTHOR]

Here, a simple, economical one-step doping strategy is adopted to prepare N, S co-doped graphene hollow spheres (NSGHS). The NSGHS exhibits remarkable oxygen-reduction-reaction (ORR) activity with a high half-wave potential (E 1/2) of 0.847 V vs. RHE and considerable long-term stability. When applied as anode materials for sodium-ion batteries (SIBs), it could deliver a high reversible capacity of 385 mAh g−1 at 500 mA g−1, excellent rate performance of 308 mAh g−1 at even 20 A g−1 and superior cycling performance at 10 A g−1 during 5000 cycles with negligible capacity fade. DFT calculation reveals that the doping of N and S endows the surrounding carbon with high positive charge and spin density, respectively, making them be highly active ORR catalytic sites except for S itself. Despite the possible oxidization of C–S–C active sites, the rest C atoms of NSGHS will still hold a considerably high catalytic activity superior to those of mono-doped or undoped cases. In addition, S doping will improve the binding between Na and graphene substrate to get a high capacity and N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites, thus the excellent stability for ORR and SIBs. [Display omitted] • A simple, economical one-step doping strategy is adopted to prepare NSGHS. • The NSGHS exhibits excellent ORR activity and Na storage performance. • The doping of N and S endows the surrounding carbon with high positive charge and spin density. • S doping will improve the binding between Na and graphene substrate to get a high capacity. • N doping effectively curbs the rising of oxygen levels and oxidization of S in C–S–C active sites. [ABSTRACT FROM AUTHOR]

Herein, the relationship between oxygen reduction reaction (ORR) catalytic activities of N-doped hollow graphene spheres (N-HGSs) and their morphologies, microstructures, and nitrogen doping configuration is deeply investigated. Based on all detection results it can be concluded that all of the level and configuration of doped-N atoms, the surface area, the mesopore structure of fabricated hollow graphene spheres related to the exposure of edges and vacancies correlating with the active sites, will ultimately affect the ORR catalytic performance of N-HGSs. Therefore, the optimized synthesis of N-HGSs can produce efficient electrocatalyst for ORR, which is better than the noble-metal Pt/C catalysts and most highly active graphene-based ORR catalysts reported to date. Additionally, the optimized synthesis of N-HGSs also exhibit excellent performance in sodium-ion storage. Because the large specific surface area, the well-connected hollow spherical and mesopore structures and the increased hydrophilicity induced by the doped-N atoms facilitate a ready transfer of charges and adsorption, diffusion and desorption of Na+ ions in and out of the active material, which could enhance sodium ion storage capacity. Additionally, expect the storage of Na+ ions by surface electro-adsorption/desorption, the insertion/extraction of Na+ through the thinner graphene shell makes a significant contribution to the improvement of sodium-ion storage capacity. Image 1 • N-doping configuration, surface area, microstructure affect ORR performance. • The mesopore structure is correlating with the ORR active sites. • The optimized N-HGSs exhibit excellent performance in ORR and sodium ion storage. • Hollow spherical and mesopore structures enhance sodium ion storage capacity. • Insertion/extraction of Na+ through thinner graphene shell enhances performance. [ABSTRACT FROM AUTHOR]

• MS-NPC is fabricated from maize straw by a simple, low-cost and convenient method. • The MS-NPC has ultra-high surface area and excellent ORR performance. • The ZAB using MS-NPC exhibits high power density and super specific discharge capacity. • The all solid-state zinc–air batteries using MS-NPC possess good flexibility. • The DFT computations verify the highly activity of MS-NPC. Rational design and preparation of waste biomass derived carbon as air electrode catalysts are pivotal for large-scale sustainable development of Zn–air battery, simultaneously promoting waste resource reuse. Herein, a three-dimensional nitrogen-doped porous graphitized carbon (MS-NPC) is designed by employing maize straw as carbon precursors. The N-doping can cause increased active sites for oxygen reduction reaction (ORR), and the FeCl 3 activated porous graphitized structure provides an efficient O 2 and electrolyte pathway toward easily access to active sites. The resultant N-doped porous graphitized maize straw carbon (MS-NPC) surprisingly exhibits high specific surface area (1483 m2 g−1), high nitrogen content (4.70%), a rather positive onset potential (0.985 V vs. RHE) and large limiting current density (5.8 mA cm−2), which is even better than most reported leading results based on biomass-derived carbon. Density-functional-theory computations confirm the synergetic effect between N-doping and FeCl 3 activated porous graphitized structure are promising to accelerate ORR process which is the essential reason for high ORR catalytic performance of MS-NPC. Furthermore, a primary Zn–air battery (ZAB) designed with MS-NPC electrode displays a maximum power density (127.9 mW cm−2), super specific-discharge-capacity (794 mAh g Zn −1 at 300 mA cm−2), longtime stability, ZnO immunity and flexible properties. Practical testing verifies that the home-made ZAB can easily power LEDs and electric fans, thereby presenting a promising strategy for the development of economical and highly active carbon as excellent ORR electrocatalyst from waste biomass. The low-cost waste maize straw is transformed to the three-dimensional nitrogen-doped porous graphitized carbon, which can be used as excellent oxygen reduction electrocatalyst for flexible zinc–air batteries, the fabrication method is simple and convenient for large-scale industrial production. Image, graphical abstract [ABSTRACT FROM AUTHOR]