Mo2C@C nanofibers film as durable self-supported electrode for efficient electrocatalytic hydrogen evolution

Self-supported electrocatalytic thin films consist 3D conducting network and well-embedded electrocatalysts, which endows the advantage in mass flow kinetics and durability for large-scale water splitting. Synthesis of such self-supported electrode still remains a big challenge due to the difficulty in the control over the 3D conducting network and the simultaneous growth of catalyst with well attachment on the conducting fibers. Herein, a self-supported Mo2C@carbon nanofibers (Mo2C@C NF) film has been successfully fabricated with outstanding electrocatalytic performance under optimized pyrolysis temperature and precursors mass ratio conditions. During the carbonation process, the Mo2C nanoparticles (~16 nm) are simultaneously grown and well dispersed on the inter-connected carbon nanofibers, which form 3D conducting network. The as-formed 3D carbon network is strong enough to support direct electrocatalytic application without additional ink or supporting substrates. This particular electrode structure facilitates easy access to the active catalytic sites, electron transfer, and hydrogen diffusion, resulting in the high hydrogen evolution reaction (HER) activity. A low overpotential of 86 mV is needed to achieve 10 mA cm-2 current density with outstanding kinetics metric (Tafel 43 mV dec-1) in 1M KOH. Additionally, the self-supported Mo2C@C NF film, a binder-free electrode, exhibits extraordinary stability of more than 340 h.

Graphene Oxide Interlayered in binder-free Sulfur Vapor Deposited Cathode for Lithium-Sulfur Battery

The main drawback of Lithium-Sulfur (Li-S) batteries which leads to a short lifetime, is the shuttle effect during the battery operation. One of the solutions to mitigate the shuttle effect is the utilization of interlayers. Herein, graphene oxide (GO) paper as an interlayer has been implemented between the sulfur cathode fabricated by the vapor deposition process as a binder-free electrode and a separator in a Li-S battery in order to gain a sufficient capacity. The morphological characteristics and electrochemical performance of the fabricated electrode have been investigated. The fabricated battery demonstrates an initial discharge capacity of 1265.46 mAh g-1 at the current density of 100 mA g-1. The coulombic efficiency is obtained to be 88.49% after 40 cycles. The remained capacity for the battery is 44.70% after several cycles at different current densities. The existence of the GO interlayer improves the electrochemical properties of the battery compared to the one with a pure sulfur cathode. The obtained results indicate that after 40 cycles, the capacity retention is 2.1 times more than that of the battery without the GO implementation.

Pd Doped Co3O4 Loaded on Carbon Nanofibers as Highly Efficient Free-Standing Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions

Self-supporting electrodes usually show excellent electrocatalytic performance which does not require coating steps, additional polymer binders, and conductive additives. Rapid in situ growth of highly active ingredient on self-supporting electric conductors is identified as a straight forward path to prepare binder-free and integrated electrodes. Here, Pd-doped Co3O4 loaded on carbon nanofiber materials through electrospinning and heat treatment was efficiently synthesized, and used as a free-standing electrode. Benefiting from its abundant active sites, high surface area and effective ionic conduction capability from three-dimensional (3D) nanofiber framework, Pd-Co3O4@CNF works as bifunctional oxygen electrode and exhibits superior activity and stability superior to commercial catalysts.