Category: Sin categoría

Posted on

New publication in collaboration with Prof. Xuanhua Li (NPU, Xi’an)

Monitoring Hydrogen Evolution Reaction Intermediates of Transition Metal Dichalcogenides via Operando Raman Spectroscopy

Adv. Funct. Mater. 2020, 2003035

A deeper understanding of the water‐splitting hydrogen evolution reaction (HER) mechanism during photocatalytic processes is crucial for the rational design of efficient photocatalysts. In particular, the HER mechanism promoted by multielement hybrid structures remains extremely challenging and elusive. Herein, an in situ photoelectrochemical/Raman measurement system is employed to monitor the HER mechanism of hybrid nanostructures under realistic working conditions via operando Raman spectra and linear‐sweep voltammetry curves. As a proof of concept, tunable composition transition metal dichalcogenides MoS2xSe2(1−x) nanosheets are used as a model photocatalyst to unveil the corresponding photocatalytic mechanism. The spectroscopic studies reveal that hydrogen atoms can be adsorbed to active sulfur and selenium atoms via intermediate species formed during the photocatalytic process. More importantly, the studies demonstrate that an exponential relationship exists between the number of reactive electrons and the Raman intensity of intermediate species, which can serve as a guideline to directly evaluate the HER performance in photocatalysts by comparing the Raman intensities of the intermediate species. As a simple, intuitive, and general analytical method, the designed operando Raman measurement approach provides a new tool for elucidating catalytic reaction mechanisms in a realistic and complex environment; and strategically improving H2 production performance of multielement photocatalysts.

Posted on

New publication in collaboration with Prof. Xuanhua Li (NPU, Xi’an)

Heat Diffusion‐Induced Gradient Energy Level in Multishell Bisulfides for Highly Efficient Photocatalytic Hydrogen Production

Adv. Energy Mater. 2020, 2001575

Insufficient light absorption and low carrier separation/transfer efficiency constitute two key issues that hinder the development of efficient photocatalytic hydrogen production. Here, multishell ZnS/CoS2 bisulfide microspheres with gradient distribution of Zn based on the heat diffusion theory are designed. The Zn distribution can be adjusted by regulating the heating rate and manipulating the diffusion coefficients of the different elements conforming the multishell photocatalyst. Because of the unique structure, a gradient energy level is created from the core to the exterior of the multishell microspheres, which effectively facilitates the exciton separation and electron transfer. In addition, stronger light absorption and larger specific surface area have been achieved in the multishell ZnS/CoS2 photocatalysts. As a result, the multishell ZnS/CoS2 microspheres with gradient distribution of Zn exhibit a remarkable hydrogen production rate of 8001 µmol g−1 h−1, which is 3.5 times higher than that of the normal multishell ZnS/CoS2 particles with well‐distributed Zn and 11.3 times higher than that of the mixed nonshell ZnS and CoS2 particles. This work demonstrates for the first time that controlling the diffusion rate of the different elements in the semiconductor is an effective route to simultaneously regulate morphology and structure to design highly efficient photocatalysts.

Posted on

Great Online UK RFB Annual Meeting – 6th July 2020

We had a great UK Redox Flow Battery Meeting yesterday, with lots of interesting talks and posters. Kathryn Toghill and the rest of the committee did an amazing job organising the event! I enjoyed listening to so much good research on flow batteries in the UK and abroad. Also, our Gengyu gave his first talk on Solar Flow Cells and got lots of interesting questions from the rest of participants. Well done Gengyu! Looking forward to the next meeting! 

Posted on

New publication with Qian in collaboration with Magda Titirici, Hui Luo and Petra Szilagyi -Trends in Chemistry

Carbon Dots in Solar-to-Hydrogen Conversion

H. Luo, Q. Guo, P. Szilagyi, A. Belen Jorge, M. Titirici, Trends in Chemistry 2020. 

Solar hydrogen production from catalytic water splitting is one of the many options available to help generate clean power and alleviate the threatening environmental concerns stemming from the use of fossil fuels. During the past decade, carbon dots (CDs) have shown great potential in their application for solar-driven hydrogen production owing to their exceptional photophysical and electrical properties derived from their sp2/sp3 hybridized core structure and rich surface functionality. In this review, we correlate the structural features of CDs with their optical and electronic properties and evaluate key properties for efficient solar energy-conversion applications with an emphasis on photocatalysis and photoelectrocatalysis, to shed some light on designing high performance CD-based photosystems.