ABSTRACT
Improving the lifetime and energy density of energy storage devices has always been a major challenge. Here, CoS2 with a hollow structure derived from zeolite-imidazolate framework-67 was reconstructed on Co(OH)F nanowires. Co(OH)F nanowires contribute to ion/electron transmission and reduce transmission resistance, thereby promoting the stability of the electrode. CoS2 with a hollow porous structure contributes to the full infiltration of electrolytes, shortens the ion transmission distance, accelerates the redox reactions, and alleviates the volume expansion, thus improving the pseudocapacitance. Therefore, the prepared Co(OH)F/CoS2 displayed excellent specific capacity (233 mAh g-1). The assembled HSC Co(OH)F/CoS2//activated carbon in KOH solution could achieve a considerable energy density (63.9 Wh kg-1). Surprisingly, the specific capacitance accounts for 107.0% of the primary capacitance (20,000 cycles), demonstrating great cycling stability. This work presents a conceptual approach for the construction of abundant and promising electrodes for HSCs.
ABSTRACT
The rapid development of portable and wearable electronics has promoted the integration of multifunction techniques. Although flexible energy storage systems have been successfully investigated, the compact configuration with photodetector and energy storage components has received less attention. As a new member of the 2D material class, MXene exhibits remarkable electronic and optical properties. Here, through the intentional introduction of ZIF-67 derivatives deposited on the Mo2CTx nanosheets, the synthesized Co-CoOx/NC/Mo2CTx heterostructure not only provided a straightforward pathway for photogenerated electrons to transport but also enhanced the structural stability of Mo2CTx, leading to a high responsivity and short rise/decay time under the illumination of simulated light in the photoelectrochemical (PEC) configuration. The integrated flexible device based on a zinc ion battery and Co-CoOx/NC/Mo2CTx heterostructure shows outstanding photodetection function and retains the intrinsic charge/discharge behaviors, which could monitor 1 day sunlight changes in real time. The paradigm presented here paves the way for realizing the development of miniaturization and multifunction toward next-generation portable and wearable technologies.
ABSTRACT
Design and construction of low-cost electrocatalysts with high catalytic activity and long-term stability is a challenging task in the field of catalysis. Metal-organic frameworks (MOF) are promising candidates as precursor materials in the development of highly efficient electrocatalysts for energy conversion and storage applications. This review starts with a summary of basic concepts and key evaluation parameters involved in the electrochemical water-splitting reaction. Then, different synthesis approaches reported for the cobalt-based Zeolitic imidazolate framework (ZIF-67) and its derivatives are critically reviewed. Additionally, several strategies employed to enhance the electrocatalytic activity and stability of ZIF-67-based electrocatalysts are discussed in detail. The present review provides a succinct insight into the ZIF-67 and its derivatives (oxides, hydroxides, sulfides, selenides, phosphide, nitrides, telluride, heteroatom/metal-doped carbon, noble metal-supported ZIF-67 derivatives) reported for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting applications. Finally, this review concludes with the associated challenges and the perspectives on developing the best economic, durable electrocatalytic materials.
ABSTRACT
Cobalt-based oxides are among the most promising electrocatalysts for oxygen evolution reactions (OER). In this context, this work reports the synthesis of manganese-doped cobaltites using the Zeolitic-Imidazolate Frameworks 67 (ZIF-67) as template. The incorporation of manganese ions into ZIF-67 structure was evaluated in ethanol and methanol, in order to obtain the best synthetic route. Non-doped (ZIF-67C) and Mn-doped cobaltites (Mn/ZIF-67C(E) and Mn/ZIF-67C(M)) were obtained after thermal treatment at 350 °C. Structural and morphological properties were investigated and presence of Mn3+ and Mn4+ was confirmed by X-ray photoelectron spectroscopy (XPS) data and magnetization curves. The electrocatalytic activity in OER was investigated in alkaline medium for manganese cobaltites, and compared to the ZIF-67C. Overpotentials to generate a current of 10 mA cm-2 were 338 mV and 356 mV for Mn/ZIF-67C(E) and Mn/ZIF-67C(M), respectively. These results are superior to those found for similar materials in the literature. The material obtained in methanol (Mn/ZIF-67C(M)) presents lower overpotential, however, shows superior electrocatalytic performance for current density above 100 mA cm-2, therefore being an efficient electrode for commercial electrolysers.