Low-dimensional Layered Rhenium Disulfide Nanosheets Photoelectrolyzed Water Application Research

A large amount of consumption of fossil fuels has resulted in an increasingly serious energy crisis and environmental pollution.It is a desire,consequently,to quest for research on new energy to alleviate the situation that has heavily relied on fossil fuels.Hydrogen is a non-carbon and clean energy source with high energy density.It possesses huge potential as an energy carrier.Electrocatalytic(EC)reduction of water through hydrogen evolution reaction(HER)with wind energy and solar energy is one of efficient and sustainable strategies for hydrogen generation.Up to date,platinum(Pt)is the most active HER catalyst,however its scarcity and high cost seriously hamper its practical utilization.In the process of exploring earth-abundant and comparable HER catalysts,layered transition metal dichalcogenides(TMDs),especially MoS2,have been proposed as a family of promising candidates because of the excellent HER activity on their unsaturated edge sites.MoS2 has been considerably investigated as electro-catalysts and co-catalysts for HER applications,whereby the activity of semiconducting MoS2 was identified to suffer from the minority edge active sites and poor intrinsic conductivity.Thus the guiding efforts have been made to engineer MoS2 catalysts with either more edge sites or higher electric conduction for improving HER activity.Despite substantial progresses,the most research has only been focused on standalone electrocatalysis,and only a few have concerned on how to integrate other driving forces especially the renewable solar light energy into HER dynamics.ReS2 was discovered to be an unique member in the TMDs family,in which the weak interlayer coupling ensures its superior photoelectric characters being independent of the number of layers.Besides,ReS2 usually crystallizes in distorted 1T' crystal structure with triclinic symmetry and gives rise to the superior electron mobility with considerable anisotropy.The Peierls distortion prevents the Bernal stacking along the c axis,leading to the much larger interlayer spacing,which can expose preferably unsaturated edge sites and access for proton permeation.Given the above structural and photoelectric benefits,few-layer ReS2 can be reasonably assumed as a novel single-component platform that naturally couples catalysis with photo-excitation forces,different from the artificial integration of light absorbers and cocatalysts in traditional PEC systems.The details are as follows:1.Identification of few-Layer ReS2 as photo-Electro integrated catalyst for hydrogen evolution.Few-layer ReS2 nanosheets(NSs)were found to have both favorable solar light harvesting and proton reducing kinetics based on the assessments for electronic band structure and Gibbs free energy(?GH*)of hydrogen adsorption.Furthermore,the naturally coupling between optical and catalytic functions was demonstrated using ReS2 NSs grown on conductive carbon fiber clothes(CFC)as a hydrogen evolution reaction(HER)cathode,where the simulated 1 sun irradiation(100 mW cm-2)could significantly improve the catalytic activity along with anodic shifts of ca.37 mV in onset potential and ca.39 mV in over potential,and near 3-fold increase in exchange current density.The comparative analyses on Tafel,turnover and active sites revealed that the light-improved HER performance was due to the photo-generated hot electron injection into edge active sites(Nano Energy,2018,48,337-344).2.Integrating ReS2 cocatalyst into p-silicon photocathodes toward enhanced solar water reduction.The ReS2 NSs were loaded on a planar p-Si surface by chemical vapor deposition(CVD)to form a p-Si/ReS2 heterostructure photocathode.The loaded ReS2 NSs significantly enhance PEC performance of p-Si.The laden ReS2 NSs not only serve as a high-activity HER catalyst but also render a suitable electronic band coupled with p-Si into a?-type heterojunction,which facilitates the photoinduced charge production,separation,and utilization.As a result,the assembled p-Si/ReS2 photocathode exhibits a 23-fold increased photocurrent density at 0 VRHE and a 35-fold enhanced photoconversion efficiency compared with the pure p-Si counterpart.The bifunctional ReS2 as a catalyst and a semiconductor enables multi-effects in improving light harvesting,charge separation,and catalytic kinetics and highlights the benefits of semiconducting catalysts integrated into PEC cells for solar-driven water splitting(ACS Appl.Mater.Interfaces 2018,10,23074-23080).3.Integrating ReS2 cocatalyst onto TiO2 nanofibers toward enhanced photocatalytic hydrogen evolution.By anchoring ReS2 NSs on TiO2 NFs through CVD method,We fabricated a large-scale three-dimensional ReS2@TiO2 heterostructure consisting of TiO2 NFs and ReS2 NSs via sequential hierarchical assemblies.The loaded ReS2 NSs significantly improved the absorption range of Ti02.The hierarchical heterojunction reduces the recombination of photogenerated electrons and holes and increases the lifetime of photogenerated carriers,resulting in the significantly enhanced photocatalytic hydrogen evolution performance.As a result,the pure Ti02 NFs have nearly zero hydrogen production under simulated sunlight(AM 1.5G),while ReS2@TiO2 heterostructure performs a recyclable hydrogen production with the high rate of 650 ?mol h-1 g-1.Overall,the fabricated ReS2 NSs improve light harvesting and photogenerated charge separation and demonstrates an application prospect of semiconductor cocatalyst in photocatalytic hydrogen evolution.