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Polymeric composite materials attracted attention when pristine polymers alone could not fulfill the necessity of high-performance functional materials for wide applications. Mixing two or more polymers (blends) together or compositing the polymers with inorganic compounds/carbon-based nanomaterials greatly solved the problem associated with the mechanical, thermal, and electronic properties along with the chemical stability, which paves a new pathway for optimizing the functional properties of active materials. However, a mere mixing of individual components sometimes would not provide enhanced properties due to the formation of phase-separated, larger domains of components. In particular, the grain boundaries of components, also known as "interfaces", actually determine the properties of these composite materials. The tuning of interfacial properties is significant to achieve composites with higher electrical conductivity and better charge transfer kinetics if they are targeted toward high-performance energy devices. This review aims to provide an overview of recent advancements in the area of polymeric composite materials with tuned interfacial characteristics towards energy conversion (solar cells, photocatalytic hydrogen production, and nanogenerators) and energy storage (supercapacitors and metal-ion batteries) devices with very recent representative examples. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Ni3S2/CNT nanocomposite can be easily synthesized using hydrothermal method. [•] The HER performance of Ni3S2/CNT nanocomposite is activated by base treatment. [•] The HER activity of nanocomposite is correlated to Ni3S2 morphology on CNTs. [•] Ni3S2 and conductive CNTs impart high HER activity and stability to the catalyst. [•] The composite electrode exhibits high catalytic activity toward glucose oxidation. [Copyright &y& Elsevier]

Abstract: Hydrogen has been proposed as a future energy carrier in the transition from the current hydrocarbon economy. Exploring advanced materials for electrocatalytic and photoelectrochemical water splitting has become one of the most important issues for bulk and inexpensive hydrogen production. In this study, the nanocomposite of MoS3 and multi-walled carbon nanotubes (MWCNTs) with the high catalytic activity toward hydrogen evolution reaction (HER) was easily synthesized using wet chemistry process. With the aid of functional groups present in MWCNTs, amorphous MoS3 nanoparticles were highly dispersed over MWCNT surface. It was found that MoS3 on the MWCNTs was electrochemically reduced to MoS2 before HER and thus the amorphous MoS2 was identified as the actual catalyst for HER. Furthermore, MoS2 with amorphous structure exhibited the higher HER activity than crystalline MoS2 due to the fact that the former had a higher number of exposed edges. In addition, the catalytic activity of nanocomposite of MoS3 and MWCNTs was increased with decreasing the loading amount of MoS3 on MWCNTs and the optimal MoS3 loading on MWCNTs was 33wt%. Based on the extensive transmission electron microscopy analysis and capacitance measurements, the catalytic activity of the nanocomposite was highly correlated to its active surface area which was controlled by MoS3 morphology on MWCNT surface. The nanocomposite of MoS3 and MWCNTs exhibited excellent HER activity with a small overpotential of ∼0.13V, large cathodic currents and a Tafel slope as small as 40mV/decade. The impedance measurements suggested that the high catalytic activity of nanocomposite of MoS3 and MWCNTs was stemmed from the synergistic effect from the highly exposed edges of amorphous MoS3 nanoparticles and the excellent electrical coupling to the conductive MWCNT network. Furthermore, it was found that the current density of this hybrid catalyst was decreased to 88% of the initial value after the continuous 500 cycling, which showed the reasonable stability in the long-term operation. The present work suggested that the highly active and stable nanocomposite of MoS3 and MWCNTs showed a great potential as a low cost alternative to Pt in water splitting. [Copyright &y& Elsevier]