No abstract

The development of noble-metal free electrocatalysts is of high importance for clean energy conversion applications. MoS2 has been considered as a promising low-cost catalyst for the hydrogen evolution reaction (HER), however its activity is limited by poor conductivity and low abundance of active sites.Moreover, its suitability as an effective catalyst for other reactions, in particluar the oxygen reduction reaction (ORR), was hardly explored to date. Herein, we show hybrid nanostructures of shelled CuS particles with MoS2 layers, which produces several outcomes: The MoS2 shell is strained and defective, and charge transfer from the core to MoS2 occurs, enabling activation of the basal plane of MoS2.Changing the feed ratio of the precursors led to control over morphology, such that the wrapping of the cores with the shell was continuously varied and characterized. We found an optimal hybrid structure, which provided high electrochemical active surface area and fast charge transfer kinetics, leading to improved activity not only towards HER (overpotential of 225 mV at 10 mA cm −2 ), but also for the sluggish ORR (onset potential 0.87 V vs RHE).

New coatings are obtained when graphene oxide is further oxidized at moderate anodic potentials (≤~1.3 V vs. Ag/AgCl). Based on a variety of spectroscopic and electrochemical observations, the coatings are attributed to the direct electropolymerization of graphene oxide sheets via oxidation of the phenol edge groups on graphene. Depending on the applied potential, ether or carboxylic groups are formed. The coatings obtained via further oxidation are characterized by a lower O/C ratio due to decarboxylation and a higher content of C=C bonds. These bonds extend aromatic conjugation into the combined graphene oxide sheets and are responsible for the highly conductive nature of these coatings.

No abstract

No abstract