Oxygen-vacancy abundant alpha bismuth oxide with enhanced cycle stability for high-energy hybrid supercapacitor electrodes

Rational synthesis of 3D coral-like ZnCo2O4 nanoclusters with abundant oxygen vacancies for high-performance supercapacitors

Transition metal oxides with high theoretical capacitance are regarded as desired electrode materials for supercapacitors, however, the poor conductivity and sluggish charge transfer kinetics constrain their electrochemical performance. The three-dimensional (3D) coral-like ZnCo2O4 nanomaterials with abundant oxygen vacancies were synthesized through a facile hydrothermal method and chemical reduction approach. The introduced oxygen vacancies can provide more active sites and lower the energy barrier, thereby facilitating the kinetics of surface reactions. Furthermore, the abundant oxygen vacancies in metal oxides can function as shallow donors to facilitate charge carrier diffusion, resulting in a faster ion diffusion rate and superior electrochemical conductivity. The electrochemical performance of ZnCo2O4 was optimized by the introduction of oxygen vacancies. The ZnCo2O4 nanoclusters, reduced by 0.5 M NaBH4 (ZnCo2O4-0.5), exhibit a specific capacitance of 2685.7 F g-1 at 1 A g-1, which is nearly twice that of the pristine ZnCo2O4 (1525.7 F g-1 at 1 A g-1). The ZnCo2O4-0.5 exhibits an excellent rate capacity (81.9% capacitance retention at 10 A g-1) and a long cycling stability (72.6% specific capacitance retention after 10 000 cycles at 3 A g-1). Furthermore, the asymmetric supercapacitor (ASC, ZnCo2O4-0.5 nanoclusters//active carbon) delivers a maximum energy density of 50.2 W h kg-1 at the power density of 493.7 W kg-1 and an excellent cycling stability (75.3% capacitance retention after 3000 cycles at 2 A g-1), surpassing the majority of previously reported ZnCo2O4-based supercapacitors. This work is important for revealing the pivotal role of implementing the defect engineering regulation strategy in achieving optimization of both electrochemical activity and conductivity.

Effectively Reinforced α-Bi2O3 MPs/PDA-RGO Sensor for Selective Modality Sensing of a Hazardous Phenolic Compound

The phenolic compound trichlorophenol (TCP) is an ingredient in fungicides and herbicides. This compound's high stability, bioaccumulation, toxicity, and poor biodegradability result in severe environmental and biological health issues. Consequently, it is crucial to have an affordable and sensitive method for detecting TCP in environmental samples. In this study, α-phase bismuth oxide microplates and polydopamine-functionalized reduced graphene oxide (α-Bi2O3 MPs/PDA-RGO) were synthesized using a simple ultrasonic method and characterized with various analytical and physical characterizations. The conversion of the catechol moieties present in the resulting PDA-RGO material into quinones facilitates productive interactions with diverse functional groups, such as hydroxyl, amine, and imine. Consequently, the compounds 2,4,6-trichlorophenol (TCP) engages in electrochemical interactions with the aforementioned functional groups. As a result, TCP shows more excellent selectivity on the designed α-Bi2O3 MPs/PDA-RGO/SPCE sensor. Under the optimized conditions, the sensor demonstrated a lower detection limit (0.0042 μM), a limit of quantification (0.0078 μM), good sensitivity (2.24 μA μM-1 cm2), a wide linear range (0.019-190.7 and 212.7-1649 μM), and pinpoint specificity. The efficacy of the sensor is additionally validated through the accurate identification of TCP residues in water, soil, and food samples.

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.

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.

Reasonably optimized structure of iron-doped cobalt hydroxylfluoride for high-performance supercapacitors

Cobalt hydroxylfluoride (CoOHF) is an emerging supercapacitor material. However, it remains highly challenging to effectively enhance the performance of CoOHF, which is limited by its poor electron and ion transport ability. In this study, the intrinsic structure of CoOHF was optimized through Fe doping (CoOHF-xFe, where x represents the Fe/Co feeding ratio). As indicated by the experimental and theoretical calculation results, the incorporation of Fe effectively enhances the intrinsic conductivity of CoOHF and optimizes its surface ion adsorption capacity. Moreover, since the radius of Fe is slightly larger than that of Co, the space between the crystal planes of CoOHF increases to a certain extent, and the ability to store ions is consequently enhanced. The optimized CoOHF-0.06Fe sample exhibits the maximum specific capacitance (385.8 F g^-1). The asymmetric supercapacitor with activated carbon achieves a high energy density of 37.2 Wh kg^-1 at a power density of 1600 W kg^-1, and a full hydrolysis pool is successfully driven by the device, indicating great application potential. This study lays a solid basis for the application of hydroxylfluoride to a novel generation of supercapacitors.

A novel Bismuth hydroxide (Bi(OH)3) semiconductor with highly-efficient photocatalytic activity

Herein, a novel Bi(OH)3 photocatalyst was successfully synthesized. Benefiting from the suitable band positions, abundant alkaline groups and oxygen vacancies, the as-prepared semiconductor exhibits efficient activity in both photocatalytic CO2...