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N, P dual‐doped porous carbon with high specific surface area of ∼2000 m2 g−1 was prepared via foaming‐carbonization process. It was demonstrated that the simple surface treatment and modification can conveniently further improve the catalytic performance of oxygen reduction reaction (ORR). The results showed that chemisorbed phosphorus can promote the surface treatment of sodium borohydride (NaBH4). The modified novel sites, adsorbing water molecules of a semi‐free state, promoted the offensive key steps of H2O molecules in ORR. After post‐treatment, the limit current density increased from 5.0 to 6.1 mA cm−2 with a decreased Tafel slope and the onset potential positively shifted. This surface‐modified catalyst was applied to Zn‐air battery and Al‐air battery, and had exhibited good applicability and excellent performances. This work illustrates that the simple post‐treatments can conveniently and effectively improve the ORR performance of metal‐free carbon catalysts. [ABSTRACT FROM AUTHOR]

A novel type of Nitrogen-Boron-Carbon ternary nanosheets (NBCs) was prepared directly from graphitic-phase carbon nitride (g-C 3 N 4 ) and achieved high yields. In these NBCs, the molar content of nitrogen and boron can exceed that of carbon, at the same time with good electronic conductivity. It was observed that there is a coexistence tendency for B/N two elements which was able to maintain the aromaticity of micro-regions. The Morphology analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrum results point to a two-dimensional conjugated dominated structure. In addition, NBCs exhibited superior electrochemical performance for ORR with much better methanol tolerance and catalytic stability than commercial Pt/C catalyst. NBCs also showed excellent catalytic activity for HER in aqueous solutions over a wide range of pH values, including acidic, neutral and alkaline conditions. These ternary nanosheets of such high N and B content has not been previously reported and potentially open up a broad research and application prospects. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The novel in-situ foaming technology from Gemini surfactant interfacial coupling. • The N, P dual-doped carbon nanosheets with multi-wrinkled surface was prepared. • As metal-free carbon catalyst for ORR, the limiting current density reached 6.7 mA/cm2 at 1600 rpm. • After about 9 h continuous test, the current density of this catalyst remained above 91%. • Wrinkles induced p z -orbital of C stretched out to bond with single electron on π 2p * orbit of O 2. Abstract N, P dual-doped carbon nanosheets was prepared by an in-situ foaming technology. The crude lecithin extracted from egg yolk was explored to prepare this novel carbon material. In the synthesis process, the crude lecithin molecular is as the Gemini surfactant and the graphitic carbon nitride (g-C 3 N 4) plays the role of self-sacrificing template. At the high temperature, the sandwich-mixture "lecithin/C 3 N 4 /lecithin" expanded and carbonized with the decomposition of g-C 3 N 4. This induces the formation of many multi-wrinkled nanosheets and synchronously constitute a multi-doped carbon foam. This unique carbon material exhibits a super-efficient catalytic activity towards oxygen reduction reaction, with the limited current density of 6.7 mA cm−2 tested at 1600 rpm in 0.1 M KOH solution, which is far larger than that of Pt/C (20%) catalyst (5.5 mA cm−2). It was demonstrated that this novel catalyst also possesses great catalytic stability. After about 9 h continuous test, the current density of this catalyst remained above 91%. These results demonstrate that the N, P dual-doped multi-wrinkled carbon nanosheets can be used as the high-efficient metal-free electrocatalyst towards oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

A novel method of introducing boron element was used to prepare a composite catalyst in which cobalt nanoparticles were embedded in N, B, and S-doped carbon matrix (Co-NBSC). This method can significantly retain the nitrogen content in the catalyst by introducing only a small amount of boron. The bonding ability of cobalt to hetero-atoms was also improved. The optimized bonding patterns between heteroatoms and metal-cobalt have further improved the performance of catalyzing the oxygen reduction reaction (ORR). Electrochemical tests show that the Co-NBSC catalyst possesses an onset potential of 0.93 ​V, a half wave potential of 0.84 ​V and a current density of 5.58 ​mA/cm2 as well as excellent stability in an alkaline solution. In addition, Co-NBSC based zinc-air battery exhibited a power density of 121.2 ​mW/cm2 and a discharge stability of more than 30 ​h. The synthesis strategy can provide new ideas for the future development of low cost non-precious metal-carbon catalyst of ORR. Novel method of increasing nitrogen contents through boron, which can effectively to improve the ORR activity. Image 1 • Novel method of increasing nitrogen content via cleverly introducing boron. • This method also promotes the formation of heteroatom-cobalt-carbon bonds. • Increased N-content and optimized bonding patterns improved ORR performances. • Onset potential of ORR was shifted positively and the Tafel slope decreased. [ABSTRACT FROM AUTHOR]

The development of trifunctional catalysts integrated with the catalytic activities of oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains an important scientific challenge. The obvious preparation strategy is to load metal-based compounds on the non-metal element doped carbon catalyst. A compact interface between heterogeneous materials is the key to obtain efficient performance. Herein, the cobalt-boron-oxide nanosheets were embedded into the N, P dual-doped carbon nanosheets, and a compact composite catalyst (Co–B–O/NPC) was constructed using boron as a medium. The Co–B–O/NPC-50% catalyst exhibits the ORR catalytic activity surpassing Pt/C catalyst, the OER catalytic activity exceeding RuO 2 , and the excellent catalytic activity of HER. These three catalytic performances originated from synergy also exhibit good stabilities. The rechargeable zinc-air battery using Co–B–O/NPC-50% as the electrocatalyst exhibits the power density of 110.7 mW/cm2 and a stable charge-discharge cycling of more than 60 h. The overall water-splitting electrolyzer using Co–B–O/NPC as sole catalyst also exhibits excellent performance and stability. A complex energy-system that combines Zn-air battery, illumination and water-splitting was built due to trifunctional characteristics. This work not only presents a novel preparation strategy, but also can deepen the understanding of the structure-activity relationship of trifunctional electro-catalysts. Image 1 • Trifunctional catalyst for oxygen reduction/oxygen evolution/hydrogen evolution. • Constructed by two heterogeneous materials linked through medium elemental-B. • Compact interfaces endow the composite catalyst with excellent trifunctionalities. • One catalyst is applicable to both zinc air battery and overall water-electrolysis. [ABSTRACT FROM AUTHOR]

• Catalyst of Se-doped FeNiP nanoparticle embedded in a carbon matrix was synthesized. • The Se atoms doped in lattice of FeNiP crystal and modulated the surface OER sites. • The Se atoms also doped in the carbon matrix and improved the ORR performance. • Se elements acting as medium elements contribute to forming a compact composite. • The assembled solid-state zinc-air batteries were integrated as a 3 × 3 module. Efficient bifunctional catalysts capable of catalyzing both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are required for the air electrode. Herein, the Se-doped FeNiP nanoparticles/N, P dual-doped carbon composite catalysts (FeNiP/SeNPC-2) were developed. The Se elements combine with various elements to form a compact heterogeneous material. At the same time, the Se-doping have modulated the crystal and surface structures, which have improved the catalytic activities of ORR and OER. The overpotential of OER was significantly negatively shifted, accompanied by a significant positive shift of the onset potential of ORR. FeNiP/SeNPC-2 has displayed an overpotential of 269 mV at the current density of 10 mA cm−2 for OER, and with a high half-wave potential (0.86 V) of ORR. The liquid zinc-air battery assembled using FeNiP/SeNPC-2 exhibited a power density of 171 mW cm−2 and stably charge-discharge cycled for 150 h. The solid-state zinc-air battery exhibited a power density of 88 mW cm−2 and stably charge-discharge cycled for 42 h. Subsequently, the solid-state zinc-air batteries of cylindrical hollow design are integrated as modules for driving devices. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Method of converting cheap wheat straw into bifunctional catalyst is developed. • Catalyst was constructed with FeCoP 2 embedding in N, P dual-doped carbon matrix. • ΔE between ORR and OER achieved 0.84 V suggests excellent bifunctional activity. • Liquid Zinc-air battery achieved 122.5 mW cm−2 and can stably cycle for 110 h. • Solid-state Zinc-air battery achieved 55.6 mW cm−2 and can stably cycle for 35 h. Transformation from crude wheat straw to the efficient bifunctional catalysts was realized to obtain a unique composite structure. The ideal designed construction of bimetallic phosphide nanoparticles embedding in N, P dual-doped carbon matrix exhibited the impressive performances for catalyzing the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This catalyst has been used to assemble metal-air batteries. The rechargeable liquid zinc-air battery achieved the power density of 122.5 mW cm−2 and charge–discharge cycled for over 110 h. The rechargeable solid-state zinc-air battery exhibited the power density of 55.6 mW cm−2 and charge–discharge cycled for over 35 h. In addition, it was also investigated in the aluminum-air battery and exhibited excellent performances. This work has paved the way of preparing efficient metal-air battery catalyst from low-cost agricultural by-products. [ABSTRACT FROM AUTHOR]

Inspired by the space mud of artificial children's toy, a shape designable carbon foam (Co-NCF) is developed. This carbon foam is endowed with ferromagnetism, oil-absorption, lightweight and has a three-dimensional network intertwined with cobalt dots, nitride graphene and fibrous carbon. Those cobalt dots are actually encapsulated in a carbon nanocage, and then modified on the nitride graphene nanosheets. The Co–N bonds are generated at the core-shell interfaces of the cobalt-carbon nanocages. The network structure of carbon foam is beneficial to the mass and charge transfer of the electrocatalysis, and the cobalt-carbon nanocages further enhance the activity of oxygen reduction reaction (ORR). These advantages endow the as-prepared Co-NCF with the excellent ORR activity and outstanding catalytic stability that exceeding the commercial Pt/C catalyst. Applied as the electrocatalyst to the zinc-air battery, Co-NCF achieves good applicability with a high output power density and discharge capacity. This work provides a novel low-cost strategy for the development of material architectures and the high-performance ORR electrocatalysts. Image 1 • Novel strategy from cellulose space-mud to designable multifunctional carbon foam. • A 3D-network intertwined with cobalt dots, N-doped graphene and fibrous carbon. • The cobalt-carbon nanocages present in Co-NCF further boost the activity of ORR. • The Co-NCF catalyst is endowed with the excellent ORR activity and good stability. • The Co-NCF catalyst is applied to zinc-air battery and expresses good applicability. [ABSTRACT FROM AUTHOR]