In recent years, a large amount of focus has been given to the development of alternative energy sources that are clean and efficient; among these, electrochemical energy holds potential for its compatibility with solar and wind energy, as well as its applications in metal-metal and metal-air batteries. However, these technologies require the use of a catalyst to make this application feasible. Current catalysts consist of precious metals such as platinum, which are expensive and block common access to electrochemical energy. Transition metals, and their oxides, serve as a promising alternative to these precious metals. A wide range of these metals, including cobalt, manganese, nickel, and iron, have been researched as bifunctional catalysts, capable of driving both the storage and discharge of energy. Not only do they show innate electrochemical capabilities, but their structural diversity, as well as their ability to be mixed, doped, and combined with other materials such as graphene, make transition metal oxides a

Oxygen reduction reaction (ORR) is one of the essential electrochemical reactions for the energy conversion and storage devices such as fuel cells and metal-air batteries. However, a large amount of Pt is required for catalyzing the kinetically sluggish ORR at the air cathode, therefore greatly limiting their large scale implementation. Development of high-performance platinum group-metal (PGM)-free ORR catalysts has been a long-term goal for such clean energy technologies. However, current PGM-free catalysts are still significantly suffering from insufficient activity and limited durability especially in more challenging acidic media, such as proton exchange membranes (PEM) fuel cells. Recently, metal-organic frameworks (MOFs), constructed from bridging metal ions and ligands, have emerged as a new type of attractive precursors for the synthesis of PGM-free catalysts, which has led to encouraging performance improvement. Compared to other catalyst precursors, MOFs have well-defined crystal structure with tunable chemistry and contain all required elements (e.g., carbon, nitrogen, and metal). Here, we provide an account of recent innovative PGM-free catalyst design and synthesis derived from the unique MOF precursors with special emphasis on engineering nanostructure and morphology of catalysts. We aim to provide new insights into the design and synthesis of advanced PGM-free

Spinel Li4Ti5O12 (LTO) and reduced graphene oxide (rGO) are attractive anode materials for lithium-ion batteries (LIBs) because of their unique electrochemical properties. Herein, we report a facile one-step hydrothermal method in preparation of a nanocomposite anode consisting of well-dispersed mesoporous LTO particles onto rGO. An important reaction step involves glucose as a novel linker agent and reducing agent during the synthesis. It was found to prevent the aggregation of LTO particles, and to yield mesoporous structures in nanocomposites. Moreover, GO is reduced to rGO by the hydroxyl groups on glucose during the hydrothermal process. When compared to previously reported LTO/graphene electrodes, the newly prepared LTO/rGO nanocomposite has mesoporous characteristics and provides additional surface lithium storage capability, superior to traditional LTO-based materials for LIBs. These unique properties lead to markedly improved electrochemical performance. In particular, the nanocomposite anode delivers an ultrahigh reversible capacity of 193 mA h g(-1) at 0.5 C and superior rate performance capable of retaining a capacity of 168 mA h g(-1) at 30 C between 1.0 and 2.5 V. Therefore, the newly prepared mesoporous LTO/rGO nanocomposite with increased surface lithium storage capability will provide a new opportunity to develop high-power anode materials for LIBs.

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The influence of polyethyleneimine (PEI) on the electrochemical behavior of cyanide-free electrolytes with 5,5-dimethylhydantoin (DMH) as a complexing agent was investigated using cyclic voltammetry (CV), chronoamperometry, and cathodic polarization measurements. The gold electrodeposition displayed three-dimensional (3-D) progressive nucleation in both the absence and presence of PEI according to the Scharifer and Hills (SH) nucleation model. With the addition of PEI, the cathodic overpotential showed an immense negative shift, and the limiting diffusion current density and the diffusion coefficient decreased. Gold electrodeposits were characterized by SEM and AFM for the micromorphology, XRD for the crystal structure, and XPS for the purity. There was preferential growth of gold crystals along the (111) crystal face in both the presence and absence of PEI, but overall growth was inhibited in the presence of PEI. The quality of the gold electrodeposit was significantly improved in the presence of PEI, with a bright golden color and high purity, smooth and compact morphology.