Double shell FeOOH/PPy on a diatomite ternary complex was assembled via two-step hydrothermal and in situ polymerization routes. The polymerization process generates chemical bonding and introduces oxygen vacancies and mesopores, enhancing the conductivity and electrochemical properties of the electrodes and ensuring structural stability.

Bimetallic phosphides have been identified as promising alternative electrode materials owing to their admirable conductivity and electrochemical activity. Nevertheless, the severe agglomeration of single-component bimetallic phosphides hinders their extensive applications. Moreover, current research lacks in-depth studies on the effect of outer/inter-component synergy on the rate capability. In this study, novel nickel cobalt phosphide nanowires on two-dimensional graphene oxide nanosheets (GO@NiCoP) were designed and prepared by combining a hydrothermal process and phosphorization. GO served as the conductive path to improve the composite conductivity and provided abundant oxygen-containing functional groups to coordinate with the metal cations of NiCoP, thereby boosting the overall structural stability. NiCoP possesses an optimal intercomponent synergistic effect, such as an optimal –OH⁻ adsorption energy and deprotonation energy, leading to an enhanced potential of the electrochemical reaction. Taking advantage of these materials, the GO@NiCoP electrode displayed a high specific capacitance of 1125 F g⁻¹ (155 mA h g⁻¹) at 2 A g⁻¹ and a high cycling stability of 104.88% capacitance retention after 5000 cycles at 30 A g⁻¹. Interestingly, the GO@NiCoP electrode delivered an exceptional rate capability of 84.09% capacitance retention at 20 A g⁻¹ and 39.77% capacitance retention at 60 A g⁻¹ owing to its stable structure and excellent conductivity. In addition, we fabricated a GO@NiCoP//AG ASC device that delivered a desirable energy density of 27.71 W h kg⁻¹ at 788 W kg⁻¹. To broaden its applications, a self-charging power system with a satisfactory lighting time was constructed using the ASC device. In short, the outstanding electrochemical performance of the electrode materials provides a novel perspective for enhancing the rate capacity of electrode materials by the outer/inter-component synergistic effect.

Al-Based LDH materials have been considered as promising active electrode materials for pseudocapacitors due to their structural tunability. In this work, we employed a hydrothermal method, alkali etching treatment, calcination and sulfofication to achieve crystalline phase transformation. According to this pathway, five materials, including CoAl LDH, Co₂AlO₄, Co(OH)₂, Co₃O₄ and Co₄S₃, have been prepared. The structural and physical/chemical properties are characterized by XRD, XPS, BET, SEM, TEM and FTIR. The electrochemical behaviors in supercapacitor and asymmetric supercapacitor (ASC) devices are characterized, respectively. As the electrode materials in supercapacitors, the specific capacitances are in the order CoAl LDH > Co₄S₃ > Co₂AlO₄ > Co₃O₄ > Co(OH)₂. The CoAl LDH exhibits the maximum specific capacitance due to the intercalation/deintercalation of electrolyte ions which is attributed to its unique layer structure. The CoAl LDH exhibits a high specific capacitance of 983.71 F g⁻¹ at 1 A g⁻¹, a superior rate capability of 79.00% at 20 A g⁻¹ and excellent cycling stability with a capacitance retention of 89.10% after 15 000 cycles. After assembling the ASC device, a maximum energy density of 16.275 W h kg⁻¹ and a high power density of 3500 W kg⁻¹ are achieved in a potential window of 1.4 V. In a word, the study not only provides a dependable pathway for materials modification, but also promotes the development of cobalt-based electrode materials for energy storage.