Unraveling the role of Ti3C2 MXene underlayer for enhanced photoelectrochemical water oxidation of hematite photoanodes

Hematite is regarded as a promising photoanode for photoelectrochemical(PEC) water splitting.However,the charge recombination occurred at the interface of FTO/hematite strictly limits the PEC performance of hematite.Herein,we reported a Ti3C2 MXene underlayer modified hematite(Ti-Fe2O3) photoanode via a simple drop-casting followed by hydrothermal and annealing processes.Owing to the bifunctional role of Ti3C2 MXene underlayer in improving the interfacial properties of FTO/hematite and providing Ti source for the construction of Fe2 TiO5/Fe2O3 heterostructure in hematite nanostructure,the bulk and interfacial charge transfer dynamics of hematite are significantly enhanced,and consequently enhancing the PEC performance.Compared with the pristine hematite,the as-prepared Ti-Fe2O3 photoanode shows an increased photocurrent density from 0.80 mA/cm^(2) to 1.30 mA/cm^(2) at 1.23 V vs.RHE.Moreover,a further promoted PEC performance including a dramatically increased photocurrent density of 2.49 mA/cm^(2) at1.23 V vs.RHE and an obviously lowered onset potential is achieved for the Ti-Fe2O3 sample after the subsequent surface F-treatment and the loading of FeNiOOH cocatalyst.Such results suggest that the introduction of Ti3C2 MXene underlayer is a facile but effective approach to improve the PEC water splitting activity of hematite.

Direct Synthesis of Co-doped Graphene on Dielectric Substrates Using Solid Carbon Sources

Direct synthesis of high-quality doped graphene on dielectric substrates without transfer is highly desired for simplified device processing in electronic applications.However,graphene synthesis directly on substrates suitable for device applications,though highly demanded,remains unattainable and challenging.Here,a simple and transfer-free synthesis of high-quality doped graphene on the dielectric substrate has been developed using a thin Cu layer as the top catalyst and polycyclic aromatic hydrocarbons as both carbon precursors and doping sources.N-doped and N,F-co-doped graphene have been achieved using TPB and F16Cu Pc as solid carbon sources,respectively.The growth conditions were systematically optimized and the as-grown doped graphene were well characterized.The growth strategy provides a controllable transfer-free route for high-quality doped graphene synthesis,which will facilitate the practical applications of graphene.

Soft X-Ray Absorption Spectroscopy of Advanced Two-Dimensional Photo/Electrocatalysts for Water Splitting

Photo/electrocatalytic water splitting has been considered as one of the most promising approaches for the clean hydrogen production. Among various photo/electrocatalysts,2D nanomaterials exhibit great potential because of their conspicuous properties. Meanwhile,synchrotron-based soft X-ray absorption spectroscopy(XAS) as a powerful and element-specific technique has been widely used to explore the electronic structure of 2D photo/electrocatalysts to comprehensively understand their working mechanism for the development of high-performance catalysts. In this work, the recent developments of soft XAS techniques applied in 2D photo/electrocatalysts have been reviewed, mainly focusing on identifying the surface active sites,elucidating the location of heteroatoms, and unraveling the interfacial interaction in the composite.The challenges and outlook in this research field have also been emphasized. The present review provides an in-depth understanding on how soft XAS techniques unravel the correlations between structure and performance in 2D photo/electrocatalysts, which could guide the rational design of highly efficient catalysts for photo/electrocatalytic water splitting.