Kang Du

Charge Transport in Two-Photon Semiconducting Structures for Solar Fuels

Semiconducting heterostructures are emerging as promising light absorbers and offer effective electron-hole separation to drive solar chemistry. This technology relies on semiconductor composites or photoelectrodes that work in the presence of a redox mediator and that create cascade junctions to promote surface catalytic reactions. Rational tuning of their structures and compositions is crucial to fully exploit their functionality. In this review, we describe the possibilities of applying the two-photon concept to the field of solar fuels. A wide range of strategies including the indirect combination of two semiconductors by a redox couple, direct coupling of two semiconductors, multicomponent structures with a conductive mediator, related photoelectrodes, as well as two-photon cells are discussed for light energy harvesting and charge transport. Examples of charge extraction models from the literature are summarized to understand the mechanism of interfacial carrier dynamics and to rationalize experimental observations. We focus on a working principle of the constituent components and linking the photosynthetic activity with the proposed models. This work gives a new perspective on artificial photosynthesis by taking simultaneous advantages of photon absorption and charge transfer, outlining an encouraging roadmap towards solar fuels.

Plasmon-dominated photoelectrodes for solar water splitting

Converting solar energy into chemical fuels through photoelectrochemical water splitting is an important technology for renewable energy development. Plasmon resonance of metal–semiconductor structures promises a great improvement of the efficiency of solar energy conversion. The principal mechanism is believed to be the spectral wavelength overlap of the photon absorbance of the semiconductor and surface resonance bands of the metal. A fundamental understanding of their structure–properties relationship has to be fully exploited for further developing efficient water-splitting techniques. This review aims to summarize design principles of plasmonic photoelectrodes and to rationalize many experimental observations. We have examined popular metal–semiconductor systems that show remarkable water-splitting performance. Three groups of plasmonic photoelectrodes are discussed in terms of their configurations, such as planar thin films, nanowire/rod arrays as well as porous structures. The physical difference and structural relationships with their photoelectrochemical performance are highlighted.

Atomic layer deposition of TiN layer on TiO 2 nanotubes for enhanced supercapacitor performance

In this paper, vertical ordered TiO2 nanotubes (TNT) with highly conductive titanium nitride (TiN) are sequentially fabricated by electrochemical anodization on Ti foils and atomic layer deposition (ALD) technique. The hollow structure of TNT and highly conductive TiN allow the electrolyte to permeate into TNT and prompt faster charge transfer. Thus, the TNT-TiN composite electrode yields the maximum specific capacitance of 10.01 mF/cm2 at a scanning rate of 1mV/s, which is 24.4 times higher than that of pristine TNT. Importantly, TNT-TiN also present outstanding cycling stability with 91.9% retention of original specific capacitance after 2000 cycles. These excellent performances showed TNT-TiN electrodes could be regarded as promising material for electrical double-layer capacitor (EDLC) or as a good scaffold material for pseudocapacitors, which should be pave a new avenue for energy storage devices.