Bismuth Nanoparticles Encapsulated in Nitrogen-Rich Porous Carbon Nanofibers as a High-Performance Anode for Aqueous Alkaline Rechargeable Batteries

Zn-induced formation of polymetallic carbonate hydroxide cathodes with high mass loading for high performance aqueous alkaline Zn-based batteries

Developing high mass loading cathodes with high capacity and durable life cycles is greatly worthwhile and challenging for alkaline aqueous rechargeable Zn-based batteries (AAZBs). Herein, we demonstrate an efficient zinc-induced strategy to rationally develop Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet array with an extremely high mass loading of 9.2 mg cm-2 on Ni foam (ZNC/NF) as such a superior cathode for AAZBs. It is discovered that Ni-Co hydroxide nanowires can be transformed into Zn-Ni-Co carbonate hydroxides/hydroxides heterostructure nanosheet with rich defect structures after the introduction of Zn during the synthetic process. The formed heterostructures and rich defect structures can enhance ion and electron transfer efficiency, thus ensuring the excellent electrochemical performance under high loading condition. Consequently, the ZNC/NF//Zn battery shows an outstanding areal capacity of 2.1 mAh cm-2 at 5 mA cm-2, with an ultrahigh energy density of 3.6 mWh cm-2. Moreover, the battery can still retain a high capacity of 0.42 mAh cm-2 after 5000 cycles at 50 mA cm-2, suggesting strong long-term cycling stability. This research enables pave the way for the rational design and manufacture of advanced electrode materials with large mass loadings.

Graphene quantum dot-mediated anchoring of highly dispersed bismuth nanoparticles on porous graphene for enhanced electrocatalytic CO2 reduction to formate

The electrocatalytic reduction of CO2 to produce formic acid is gaining prominence as a critical technology in the pursuit of carbon neutrality. Nonetheless, it remains challenging to attain both substantial formic acid production and high stability across a wide voltage range, particularly when utilizing bismuth-based catalysts. Herein, we present a novel graphene quantum dot-mediated synthetic strategy to achieve the uniform deposition of highly dispersed bismuth nanoparticles on porous graphene. This innovative design achieves an elevated faradaic efficiency for formate of 87.0% at -1.11 V vs. RHE with high current density and long-term stability. When employing a flow cell, a maximum FEformate of 80.0% was attained with a total current density of 156.5 mA cm-2. The exceptional catalytic properties can be primarily attributed to the use of porous graphene as the support and the auxiliary contribution of graphene quantum dots, which enhance the dispersion of bismuth nanoparticles. This improved dispersion, in turn, has a significantly positive impact on CO2 activation and the generation of *HCOO intermediates to facilitate the formation of formate. This work presents a straightforward technique to create uniform metal nanoparticles on carbon materials for advancing various electrolytic applications.

Hierarchical bismuthyl bromide microspheres assembled by laminas as efficient negative material for aqueous alkali battery

Bismuth (Bi) based compounds are promising negative materials in aqueous alkali batteries (AABs) for the 3-electron redox chemistry of Bi element within low potentials, the exploration of new Bi-based negative materials is still a meaningful work in this field. Herein, a hierarchical bismuthyl bromide (BiOBr) microspheres material assembled by laminas was prepared via solvothermal reaction and attempted as negative battery material for AAB. The pronounced redox reactions of Bi species in low potential enable high battery capacity, and the porous texture with high hydrophilicity facilitates diffusion of OH- and participation in faradaic reactions. When used as negative battery electrode, the BiOBr could offer decent specific capacity (Cs, 190 mAh g-1 at 1 A g-1), rate capability (Cs remained to 163 mAh g-1 at 8 A g-1) and cycleability (85% Cs retention after 1000 charge-discharge cycles). The AAB based on BiOBr negative electrode could export an energy density (Ecell) of 61.5 Wh kg-1 at power density (Pcell) of 558 W kg-1 and good cycleability. The current work showcases valuable application expansion of a traditional BiOBr photocatalyst in battery typed charge storage.

Bi-MOF-Derived Carbon Wrapped Bi Nanoparticles Assembly on Flexible Graphene Paper Electrode for Electrochemical Sensing of Multiple Heavy Metal Ions

The development of nanohybrid with high electrocatalytic activity is of great significance for electrochemical sensing applications. In this work, we develop a novel and facile method to prepare a high-performance flexible nanohybrid paper electrode, based on nitrogen-doped carbon (NC) wrapped Bi nanoparticles (Bi-NPs) assembly derived from Bi-MOF, which are decorated on a flexible and freestanding graphene paper (GP) electrode. The as-obtained Bi-NPs encapsulated by an NC layer are uniform, and the active sites are increased by introducing a nitrogen source while preparing Bi-MOF. Owing to the synergistic effect between the high conductivity of GP electrode and the highly efficient electrocatalytic activity of Bi-NPs, the NC wrapped Bi-NPs (Bi-NPs@NC) modified GP (Bi-NPs@NC/GP) electrode possesses high electrochemically active area, rapid electron-transfer capability, and good electrochemical stability. To demonstrate its outstanding functionality, the Bi-NPs@NC/GP electrode has been integrated into a handheld electrochemical sensor for detecting heavy metal ions. The result shows that Zn²⁺, Cd²⁺, and Pb²⁺ can be detected with extremely low detection limits, wide linear range, high sensitivity, as well as good selectivity. Furthermore, it demonstrates outstanding electrochemical sensing performance in the simultaneous detection of Zn²⁺, Cd²⁺, and Pb²⁺. Finally, the proposed electrochemical sensor has achieved excellent repeatability, reproducibility, stability, and reliability in measuring real water samples, which will have great potential in advanced applications in environmental systems.

Bismuth oxyformate microspheres assembled by ultrathin nanosheets as an efficient negative material for aqueous alkali battery

A negative electrode with high capacity and rate capability is essential to match the capacity of a positive electrode and maximize the overall charge storage performance of an aqueous alkali battery (AAB). Due to the 3-electron redox reactions within a wide negative potential range, bismuth (Bi)-based compounds are recognized as efficient negative electrode materials. Herein, hierarchically structured bismuth oxyformate (BiOCOOH) assembled by ultrathin nanosheets was prepared by a solvothermal reaction for application as negative material for AAB. Given the efficient ion diffusion channels and sufficient exposure of the inner surface area, as well as the pronounced 3-electron redox activity of Bi species, the BiOCOOH electrode offered a high specific capacity (C_s, 229 ± 4 mAh g^-1 at 1 A g^-1) and superior rate capability (198 ± 6 mAh g^-1 at 10 A g^-1) within 0 ∼ -1 V. When pairing with the Ni₃S₂-MoS₂ battery electrode, the AAB delivered a high energy density (E_cell, 217 mWh cm^-2 at a power density (P_cell) of 661 mW cm^-2), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.

P-Orbital Bismuth Single-Atom Catalyst for Highly Effective Oxygen Electroreduction in Quasi-Solid Zinc-Air Batteries

P-block metals have gradually been utilized to synthesize non-noble-metal catalysts for oxygen reduction reaction (ORR) due to the easily tunable localized p-orbitals and resulted versatile electronic structures. The high-density single-atom bismuth sites (Bi-NC) anchored onto nitrogen-doped three-dimensional porous carbon are proved to possess significant electrocatalytic ORR performance. Theoretical calculations unveil positively charged bismuth centers prominently improved the adsorption capacity of N-doped carbon to O₂ . The p orbitals of Bi sites within Bi-NC easily generate hybrid states with p orbitals of O₂ , thus promoting charge transfer and ultimately reducing the energy barrier of ORR. Benefiting from p-orbital electrons regulation of bismuth atoms, Bi-NC exhibit ORR half-wave potential of 0.86 V (vs RHE). Additionally, both liquid and quasi-solid zinc-air batteries with Bi-NC as air-cathodes achieve higher power density and specific capacity than 20 wt% Pt/C, and comparable stability and round-trip efficiency with 20 wt% Pt/C. The discovery sheds light on the theoretical and practical guidance for p-block metallic single-atom catalysts.

Hierarchical Heterostructure Engineering of Layered Double Hydroxides on Nickel Sulfides Heteronanowire Arrays as Efficient Cathode for Alkaline Aqueous Zinc Batteries

Aqueous alkaline rechargeable nickel-zinc (Ni-Zn) batteries possess great potential for large-scale energy storage systems because of their high output voltage, cheap cost, and intrinsic safety. However, the practical applicability of Ni-Zn batteries has been limited by traditional Ni-based cathodes with low capacity and poor cycle stability. Rational design of electrode structure and composition is highly desired but still significantly challenging. Herein, uniform self-supported hierarchical heterostructure composites interacting NiCo-layered double hydroxide with 1D nickel sulfides heteronanowire rooted on Ni foam (NF\Ni₃ S₂ /NiS@NiCo-LDH) are successfully developed by a hydrothermal sulfurization-electrodeposition process. The self-supported 3D hierarchical heterostructured composites nanoarray provides abundant reactive sites, rapid ion diffusion channels, and fast electron transfer routes, as well as strong structural stability. More significantly, the strong interfacial charge transfer between Ni₃ S₂ /NiS heteronanowire and NiCo-LDH effectively modifies the electronic structure of the composites and thereby improving the reaction kinetics. Consequently, the NF\Ni₃ S₂ /NiS@NiCo-LDH electrode presents a superior capacity of 434.5 mAh g^-1 (1.73 mAh cm^-2 ) at 3 mA cm^-2 . In addition, the fabricated NF\Ni₃ S₂ /NiS@NiCo-LDH//Zn battery can offer a maximal energy density and power density as large as 556.3 Wh kg^-1 and 26.3 kW kg^-1 , respectively, as well as an exceptional cycling performance.