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The strategy of heteroatom doping and metal active sites can synergistically promote oxygen electrocatalysis. Especially, the combination of theoretical simulations with experimental results provides new opportunities to understand the electrocatalytic mechanism. Herein, the 3D carbon nanosheets aggregate with highly branched carbon nanotubes and cobalt active sites (CoCNTs/PNAs) is prepared via the facile self‐assembly‐pyrolysis strategy. The CoCNTs/PNAs electrocatalysts exhibit superior bifunctional activities to oxygen reduction (E1/2 = 0.925 V) and evolution (Ej = 10 = 1.54 V) reactions, surpassing those of Pt/C‐RuO2 catalysts. The theoretical calculations reveal that the electronic interaction of cobalt sites and nitrogen‐doped carbon matrix plays a critical role in boosting the bifunctional electrocatalytic performance. Additionally, the rechargeable Zn‐Air battery (ZAB) assembled with aqueous electrolyte exhibits the largest power density of 371.6 mW cm−2 and outstanding cycling durability (over 2000 h). Furthermore, all‐solid‐state cable‐type ZAB delivers high flexibility with good cycling stability and high energy efficiency (76.5%). This work will open a new avenue to adjust the metal‐carbon support interaction for functional electrocatalysis via hierarchical porous structure design. [ABSTRACT FROM AUTHOR]

Vacancy engineering is one of the most effective strategies to introduce defects for improving electrocatalytic activities of cobalt oxides. Recent intensive research has been conducted to introduce oxygen vacancies for boosting Li–O2 battery performance. However, it is difficult to examine the efficiency of cationic vacancies due to their complicated preparation. Herein, a feasible method is demonstrated to introduce cationic vacancies into cobalt oxides via the thermal treatment of glycerolatocobalt (GlyCo) nanostructure. The formation of GlyCo composed of the repeating CoOCoO units provides the possibility to regulate the ratio between cobalt and oxygen, thus cobalt vacancies in cobalt oxides can be easily created by the thermal treatment. The presence of cobalt vacancies enables the regulation of electronic structure and charge‐transport properties of cobalt oxides with abundant defects on the basis of the experimental results and theoretical calculations, thus improving electrocatalytic activities. Therefore, the Li–O2 battery delivers superior electrochemical performance with large specific capacities of 13 331/12 040 mAh g−1, low overpotentials for the oxygen evolution reaction/oxygen reduction reaction of 1.15/0.23 V and good cycling stability. This work provides a favorable method to create metal vacancies for improving catalytic efficiency of advanced energy materials. [ABSTRACT FROM AUTHOR]

Selenium-sulfur solid solutions are a class of potential cathode materials for high energy batteries, since they have higher theoretical capacities than selenium and improved conductivity over sulfur. Here, a high-performance cathode material by confining 70 wt% of SeS2 in a highly ordered mesoporous carbon (CMK-3) framework with a polydopamine (PDA) protection sheath for novel Li-Se/S batteries is reported. With a relatively high SeS2 mass loading of 2.6-3 mg cm−2, the CMK-3/SeS2@PDA cathode exhibits a high capacity of >1200 mA h g−1 at 0.2 A g−1, excellent C-rate capability of 535 mA h g−1 at 5 A g−1, and prolonged life over 500 cycles. Benefitting from the unique advantages of SeS2 and the rationally designed host framework, this new cathode material demonstrates a feasible strategy to overcome the bottlenecks of current Li-S systems for high energy density rechargeable batteries. [ABSTRACT FROM AUTHOR]

Deoxyribonucleic acid (DNA) is used to functionalize graphene and to further guide the growth of ultrasmall palladium (Pd) nanocrystals with uniform distribution on graphene (Pd‐DNA@Graphene), demonstrating greatly improved electrocatalytic performance towards formic acid oxidation for direct formic acid fuel cells. [ABSTRACT FROM AUTHOR]

The development of highly efficient and durable electrocatalysts is crucial for overall water splitting. Herein, the in situ scaffolding formation of 3D Prussian blue analogues (PBAs) on a variety of 2D or 1D metal hydroxides/oxides to fabricate hierarchical nanostructures is first demonstrated. Typically, cobalt hydroxide or oxide nanoarrays are used as the precursor and structural oriented template for the subsequent growth of 3D PBA nanocubes. The mechanism study reveals that the interfacial scaffolding process can be reversibly controlled via the in situ ion exchange process with adjusting coordination ions. Thus, the facile, versatile strategy can extend to successfully fabricate a variety of hierarchical PBA‐based nanostructures including on cobalt fluoride hydroxide, copper hydroxide, monometal or bimetal nickel–cobalt hydroxides, cobalt oxide, and manganese oxide nanosheets with structural tailor‐ability and chemical diversity. More interestingly, the metal nitride derivatives obtained via controlled calcination process exhibit good electrocatalytic activity for water splitting with low overpotentials, and remarkable durability for 1200 h, thanks to the superior intrinsic activity of bimetal nature and the scrupulous hierarchical structure. This versatile strategy provides a paradigm for rational design of PBA‐based functional nanomaterials, which is highly promising in energy conversion, storage, and electrocatalytic fields. The in situ scaffolding approach is first developed for the growth of 3D Prussian blue analogues on various 2D or 1D metal hydroxides/oxides to fabricate hierarchical nanostructures via the reversible in situ ion exchange process, which renders the fabrication of hierarchical metal nitride derivatives with good bifunctional electrocatalytic activity and remarkable durability for overall water splitting. [ABSTRACT FROM AUTHOR]