2D, 3D Nanostructure Materials for Electrochemical Energy Storage and Conversion

Abstract

Energy is an essential factor for sustainable development and poverty eradication. Due to the growing of global energy demand and increasing levels of greenhouse gases and pollutants, scientists nowadays are paying a huge attention to establish a new energy technology, which is clean, environmentally friendly, and cost effective. In my doctoral research, I have demonstrated on the development of 2D and 3D nano structure materials for energy storage and energy conversion technology in the lithium rechargeable batteries (Li-X batteries; X=S,Se) field, electrochemistry such as water splitting: oxygen evolution reaction, hydrogen evolution reaction (HER, OER) and oxygen reduction reaction (ORR). In chapter 1, we introduced about two-dimensional transition metal dichalcogenides. We discuss about the background, general information about synthesis methodology, physical/chemical properties, and potential applications of two-dimensional transition metal dichalcogenides. Similarly, we also introduced about three-dimensional nanostructure materials Prussian Blue and Metals-based Prussian Blue. It provided information about the current research state of Prussian Blue and Metals-based Prussian Blue as preparation methods and application fields. Moreover, we have discussed about the tendency of research about energy storage and energy conversion technology. In chapter 2, we introduced a new strategy to fabricate multi-layered graphene structure embedding in situ generated selenides active cathode materials for high-power Li-Se battery by exploiting the MoSe2- multilayered graphene (Gr- MoSe2) structure. The MoSe2 has been synthesized by applying a reflux system and selenoacetamide were used as Se precursor without using any reduced reagent. Moreover, this strategy also introduced the generation in situ a layer of graphene in the interlayer of MoSe2, which improves the Litium -Selenium battery’s performance. Moreover, the shuttle effects can be effectively controlled, and the multi-layered graphene structure becomes a promising cathode platform for Li-Se batteries. In chapter 3, we presented a strategy to successfully synthesize the hybrid MoS-Se-multilayered graphene (MoS-Se-Gr) composite by applying a closed reflux system with two different S and Se precursor ratios of 1:1 and 5:1, then multilayered graphene was formed by calcination processes in inert conditions. The multi-layered graphene structure generated an in situ SSe active cathode material for high performance and long cycling life Li/S-Se battery by electrochemically reduction (lithiation) of MoS-Se-multilayered graphene (MoS-Se-Gr) structure. The multilayered graphene became an ideal platform to reduce shuttling effects by providing the space for the formation of intermediate lithium S-Se during discharging/charging processes. In addition, with the existence of multilayer graphene and the hybrid structure of coupled S and Se in composite materials improves electrical properties and reduce the internal resistance of cathode for getting high capacities and long cycle lifetime of Lithium /Sulfur-Selenium battery. In chapter 4, we developed an aqueous-solution based chemical transformation approach for the formation of cobalt hexacyanoferrate (Co-HCF= Co3[Fe(CN)6]2). Cobalt hexacyanoferrate has been deposited as a Prussian blue analog metal–organic-framework on a substrate using an ion-exchange chemical transformation route. When the Co-HCF film was investigated as a catalyst for electrochemical oxygen evolution reaction (OER). The Co-HCF crystals has demonstrated the superior electrocatalytic performance on water-oxidation from alkaline and neutral electrolytes, which is competitive to the catalytic performance demonstrated by the many outstanding water-oxidation catalysts.

In chapter 5, we designed the thin film of nickel based Prussian blue analog hexacyanoferrate (Ni-HCF: Ni3[Fe(CN)6]2), particularly via electrochemical anodization route. Hydrogen is one of the friendly fuels to the environment, and the most widely used in key industrial process. Consequently, hydrogen is going to play an important role in energy carrier economy in the future. The production of molecular hydrogen by electrochemical splitting of water is becoming very promising for the development of clean energy technology. Unfortunately, the cathodic process for hydrogen evolution reaction (HER) in electrochemical water splitting devices are traditionally facilitated by noble metals such as platinum. However, due to the rising cost of platinum, significant advances have been achieved to identify HER electrocatalysts in alternate to platinum. The obtained Ni-HCF film achieved high performance for electrochemical hydrogen evolution reaction, suggesting an interesting candidate and promising routes for identifying highly active HER electrotrocatalysts with high performance for electrochemical HER in 1 M KOH electrolyte with the long-term electrochemical durability. Furthermore, this work reports on designing the metal-HCF electrode based on full-water splitting device consisting of the binder-free Ni-HCF film on Ni-plate and Co-HCF film on carbon paper, as HER and OER electrodes, which is promising for overall water splitting.