Photocatalytic Performance Of Mo-based/Cu-based Cocatalysts Modified TiO₂

Recent years,solar fuels as the clean and renewable energy have attracted the attention of many researchers owing to the increasingly serious energy shortage and environmental pollution.Solar fuels are H2 coming from photocatalytic water splitting and carbon compounds obtained from photocatalytic CO2 reduction,and their preparation is mainly based on semiconductors i.e.photocatalysts.Since 1972,TiO2 was first employed on the reaction of water splitting by working as one photoanode.After that,owing to its stable chemical properties,non-toxicity,and low cost,TiO2 has attracted widespread attention.However,there are two major problems limiting its application,the low visible light utilization and high photogenerated carrier recombination rate.This paper aims to solve the mentioned two problems.The Mo-and Cu-based cocatalysts were developed to modify TiO2.The 3d metals(Fe,Co,Ni and Cu)were used to modulate the Mo2C work function and the Pt was employed to synthesize the bimetallic Cu-Pt surface co-catalysts.This paper focuses on the preparation method,performance measurements and reactions mechanism of TiO2-based photocatalysts.The detailed results of this paper are below:(1)Work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The effects of the type of 3d metal and the concentration of doped metal on the catalytic activity were investigated.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,10%Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV and the corresponding Tafel slope values are 40 mV/dec.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Cu-Mo2C-TiO2 has the best photocatalytic HER rate of 521 umol/h.Further investigate the internal driving force of the improved catalytic activity.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst-solution interface.(2)Based on the previous study,It can be seen that the doped element of Cu obtained the best catalytic activity and further study the copper-based materials was carried out.Herein,we report a strategy for boosting the solar fuel generation rate of TiO2 by loading co-catalysts(bimetallic Cu-Pt and CuO)via a two-step photodeposition processes.The sample of Cu-Pt/TiO2-CuO shows a photocatalytic H2 generation rate of 173.7 umol/g*h under simulated sunlight conditions.For the photocatalytic CO2 reduction by water,the sample of CuPt/TiO2-CuO shows the release of H2,O2,CO,CH4,and CH3OH,whereby CO is the main reaction product.Typically,the yields CO are 2.1 and 3.2 umol/h*g under LED-405 and LED-425 nm,respectively;the CO2-to-CO conversion ratios with respect to separated carriers are 73.8%and 76.19%.