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Due to the intrinsic safety and cost effectiveness, aqueous Zn‐ion batteries (AZIBs) are considered a promising candidate for future energy storage systems. However, the widespread implementation of AZIBs faces significant obstacles due to various undesirable side reactions, including hydrogen evolution reaction (HER), corrosion, and uncontrolled dendrite growth at the anodes. Here, 4‐hydroxybenzoic acid sodium salt (PHB) is employed in the ZnSO4 electrolyte to enable highly‐reversible zinc anodes. PHB has a greater tendency to bind with the Zn surface, resulting in increased steric effects within the electrolyte. As a result, it hinders the direct interaction between anode and water while facilitating the uniform plating of Zn2+. Zn/Zn batteries with PHB additives realized more than 1600 h stable cycling life under 1 mA cm−2 and 1 mAh cm−2. Moreover, Zn/Cu batteries with PHB additives achieved a reversible plating/stripping process for over 500 cycles with high average CE of 98.6 %. In addition, the assembled Zn/NH4V4O10 batteries with PHB additive yielded 80.5 mAh g−1 after 1000 cycles at 10 A g−1. The inexpensive and effective application of PHB as an electrolyte additive has the potential to significantly enhance the stability and dependability of ZIBs. [ABSTRACT FROM AUTHOR]

Ni/Co diatomic clusters supported on nitrogen-doped carbon foams are prepared via molten salt method to improve the density of surface active sites of zinc-air battery catalysts and further explore metal-modified carbon-based catalysts. The influence of Co and Ni atoms on the carbon foam structure is investigated by X-ray diffraction and high-resolution electron microscopy, and the presence of metal atoms in N-doped carbon foams is confirmed by X-ray spectroscopy. The left shift of the diffraction peak of Co doped graphitic carbon indicates an increase in the interlayer spacing and a reduced graphitization degree, while the introducton of Ni atoms promotes graphitization. For Ni–Co/NFC -2 , Ni inhibits the insertion of Co in carbon layer by increasing graphitization, thus exposing more Co-active substances on the surface, which is important for improving the catalytic process of ORR and OER. According to electrochemical tests, Ni–Co co-doped carbons exhibited superior bi-functional electrocatalytic performance with oxygen reduction reaction (ORR) E onset = 0.97 V and a Tafel slope of 49.5 mV dec−1, accompanied by oxygen evolution reaction (OER) E j = 10 mA cm −2 = 1.46 V. Zinc-air battery (ZAB) cell, utilizing the developed material as a catalyst, exhibited a high discharge power density of 138 mW cm−2 with stable performance for up to 200 h. [Display omitted] • Ni inhibits the insertion of Co in carbon layer by increasing graphitization. • This effect promotes the more Co active sites formed on the surface. • The assembled zinc-air battery exhibits high power density and cycle stability. [ABSTRACT FROM AUTHOR]

The construction of a hybrid hierarchical architecture is a promising strategy for optimizing the electrocatalytic activity and the performance of flexible Zn-air battery. However, it still remains a challenging task. This study reports on the use of a simple approach in the preparation of a flexible 3D self-supporting bifunctional catalyst. Ultrathin NiFe-based layered double hydroxide nanosheets (NiFe-LDH) have in this approach been strongly coupled to a metal-organic framework (MOF)-derived carbon nanoflake array, to be used in flexible Zn-air batteries. Importantly, the introduction of Co nanoparticles that were anchored onto the nitrogen-doped porous carbon (Co-NC) nanoflakes provided an abundance of active sites for the oxygen reduction reaction (ORR). Moreover, the catalytic oxygen evolution reaction (OER) process was improved by altering the local electronic structure of the Ni and Fe species in NiFe-LDH. The 3D interconnected conductive network structure, in addition to the strong coupling between NiFe-LDH and Co-NC, was found to give a catalyst with superior electrocatalytic OER performances. The overpotential was only 284 mV at 50 mA cm−2 in an alkaline medium, which is a result that outperforms the commercial RuO 2 catalyst. This bifunctional catalyst did also exhibit a good catalytic performance that is comparable to that of commercial Pt/C towards ORR. Interestingly, when this catalyst was used as binder-free air cathode, the assembled flexible solid-state Zn-air battery demonstrated a favorable power density, cycling stability, and mechanical flexibility. The present work offers a facile and efficient strategy for the development and construction of self-supporting bifunctional OER/ORR electrocatalysts, to be used in wearable and flexible electronic devices. [Display omitted] • A 3D self-supporting bifunctional catalyst is reported for flexible Zn-air batteries. • The as-prepared catalyst displays superb electrocatalytic ability for OER/ORR. • This work offers an efficient strategy of structural engineering for constructing new catalysts. [ABSTRACT FROM AUTHOR]

Rampant side reactions such as hydrogen evolution reaction (HER), corrosion and uncontrollable dendrite growth at anodes greatly impede the application of AZIBs. Herein, caprolactam (CPL) is employed as a crucial electrolyte medium to achieve the aim of highly reversible zinc anodes. CPL molecules exhibit a lower adsorption energy (−1.94 eV) than H 2 O and preferential binding with Zn anodes, resulting in a H 2 O-poor anode/electrolyte interface and an enhanced steric effect at the anode surface. This effect effectively hinders the contact between zinc metal and water molecules, consequently facilitating the uniform and controlled deposition of Zn2+. Furthermore, the combination between CPL and Zn2+ contributes to the optimization of solvation structures. Consequently, Zn/Zn batteries with CPL additives realized more than 2100 h stable cycling life under 1 mA cm−2 and 1 mAh cm−2. Moreover, Zn/Cu batteries with CPL additives achieved a reversible plating/stripping process for over 3000 cycles with high average CE of 99.4%. Besides, the assembled Zn/NH 4 V 4 O 10 full batteries using electrolyte of ZnSO 4 /CPL also exhibited excellent cyclic performance. The batteries yielded 77.1 mAh g−1 under the current density of 5 A g−1 after 1000 cycles. CPL demonstrates significant potential as a cost-effective and multifunctional electrolyte additive for achieving stable and reliable AZIBs. • Caprolactam (CPL) is proposed as a multifunctional electrolyte additive for AZIBs. • Theoretical calculations predict the mechanisms of CPL on Zn anodes. • CPL would effectively adsorb and form a protective layer on Zn anodes. • CPL would enhance the steric effect and promote the homogeneous deposition of Zn2+. • CPL would regulate the coordination environment of Zn2+ in the electrolyte. [ABSTRACT FROM AUTHOR]

The hollow materials with open structure can accelerate the mass transfer and bubble release rate, which have attracted tremendous attention for electrocatalytic water splitting. In this work, a unique tri-metal phosphide open nanotube structure [FeCoNiP@carbon quantum dots, FCNP@CQDs] is firstly fabricated by a selected etching and phosphating process with a MIL-88A@CQDs (MIL stands for Material of Institute Lavoisier) as the precursor. Benefiting from their open structure, FCNP@CQDs exhibit excellent catalytic performance. In alkaline seawater solution, a low overpotential of 268 mV is required to reach 20 mA cm−2 current density for oxygen evolution reaction, while the η 20 of hydrogen evolution reaction is 150 mV. The FCNP@CQDs//FCNP@CQDs electrolyzer requires a voltage of 1.61 V to reach 10 mA cm−2. The integrated strategy of CQDs-doping and construction of hollow open structures may open a new and relatively unexplored path for fabricating high-performance seawater splitting catalysis. [Display omitted] • The open hollow FCN-LDHs@CQDs nanotube is firstly prepared via MOF etching process. • Open hollow structure can accelerate the mass transfer and bubble release. • The involved CQDs and defects can optimize the intrinsic activity of active species. • XPS and in-situ Raman confirm the phase evolution process of anode electrode. [ABSTRACT FROM AUTHOR]

The development of phosphide-based electrocatalyst with excellent properties and good stability under both acidic and alkaline condition is the hotspot of recent research. Herein, we synthesized N doped CoP coated with carbon nanotubes (CoP@NC) electrocatalyst for hydrogen evolution reaction (HER), in which, the ZIF-67 (ZIF = zeolite imidazole skeleton) nanoparticles wrapped Co-MOF (MOF = metal-organic skeleton) nanorods has been used as precursor. The improvement of catalytic performance of N-doped CoP can be attributed to the fact that the introduction of N can optimize the electronic structure and the in-situ grown carbon nanotubes can improve charge transfer rate and avoid the agglomeration of active units. In addition, the effect of phosphorization temperature and the amount of carbon nanotube on the electrochemical activity of the samples were also investigated, and the obtained CoP@NCs only required low overpotential of 250 mV and 234 mV to drive the current density of 100 mA cm−2 under acidic and basic conditions, respectively. This work opens up an efficient paradigm for optimizing the performance of electrocatalysts. • N doped CoP coated with carbon nanotubes (CoP@NC) has been synthesized. • The in-situ formed carbon nanotubes could efficiently improve the charge transfer rate. • The use of Co-MOF in the core part could efficiently the accumulation of active phase. • The carbonization atmosphere has an obviously effect on the electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Precise adjustment of the electronic structure of conductive MOFs load materials plays an important role in the design of electrocatalysts. In this paper, a hydrogen evolution catalyst in the full pH range was prepared by using a rapid microwave method to partially carbonize conductive MOFs materials and quickly anchoring small metal Ru nanoparticles on them. [Display omitted] • Ru@p-Co 3 HHTP 2 is quickly prepared by a microwave solid-phase pyrolysis method. • Partial carbonization and SMSI in microwave improves stability and reactivity. • This catalyst has excellent hydrogen evolution performance in the full pH range. • DFT calculations and experiments revealed the synergy between Ru and p-Co 3 HHTP 2. Conductive metal organic frameworks (MOFs) have limited their long-term development in the actual electrocatalytic test process due to their low activity and poor stability. Here, for the first time, ultra-small Ru nanoparticles supported by a novel conductive MOF material (Co 3 HHTP 2) were synthesized simply and quickly (60 s) using only a household microwave oven. In this process, the conductive MOF is partially carbonized, strong metal carrier interaction (SMSI) is generated, and Ru nanoparticles are firmly attached to the carrier to form Ru@p-Co 3 HHTP 2. The Ru@p-Co 3 HHTP 2 -3.2% catalyst has excellent hydrogen evolution performance in the full pH range. Density functional theory calculations (DFT) result shows that the partial carbonization of the conductive MOF and the presence of SMSI promote the charge transfer at the interface between Ru nanoparticles and Co 3 HHTP 2 , which not only synergistically accelerates the water dissociation step and reduces the hydrogen adsorption energy, but also enhances the stability of the catalyst. [ABSTRACT FROM AUTHOR]