The Photoelectrochemical Performance Of Molecular Catalysts On The Surface Of Bismuth Vanadate Semiconductor

At present,the fossil energy plays an important part in the global energy provision.However,the use of fossil fuels has already caused serious environmental problems.Therefore,finding a clean,environmental friendly energy source has become an urgent need for us.Utilizing solar energy is obviously the most feasible long-term solution.Artificial photosynthesis can convert solar energy into chemical energy effectively.An effective method to achieve artificial photosynthesis is to establish a photoelectrochemical cell capable of absorbing visible light,in which a water oxidation reaction occurs at the anode,and hydrogen reduction or carbon dioxide reduction occurs at the cathode.In a PEC device,the oxygen evolution reaction?OER?in photoanode as the key half reaction is generally considered as the bottleneck,due to its multiple electrons and protons processes which are thermodynamically demanded.So,one of the barriers that needs to be overcome prior to a widespread use of this technology is the development of stable and efficient photoanodes.In this work,we present two BiVO₄ photoanodes modified with cobalt salophen?Co?salophen??complexes for PEC water oxidation.The resulting photoanodes show significantly enhanced PEC performance.Under simulated sunlight illumination(AM1.5 G,100 mW cm^-2),high photocurrents of 3.89 mA cm^-2 and 4.27 mA cm^-2 were obtained for Co1/BiVO₄ and Co2/BiVO₄ respectively at 1.23 V?vs.reversible hydrogen electrode?RHE??in a neutral solution,an almost three-fold enhancement over that of the unmodified BiVO₄.Intensity-modulated photocurrent spectroscopy?IMPS?analysises show that the Co?salophen?complexes,not only accelerate the water oxidation reaction,but also reduce the surface recombination.The half-cell solar energy conversion efficiencies for Co1/BiVO₄ and Co2/BiVO₄ were 1.09%and1.18%at 0.7 V,respectively.Due to their hydrophobic nature,the Co?salophen?complexes can bind strongly to the surface of BiVO₄.When the Co2 complex featuring four hydrophobic tert-butyl groups in salophen ligand was anchored to BiVO₄,an extremely stable photocurrent of more than 3.5 mA cm^-2 at 1.23 V vs.RHE is sustained for at least 3 h without decay.Such a stable and robust photoanode based on molecular WOC surpass those attained by most of the state-of-the-art heterogeneous catalysts.In addition,the CoF16Pc catalyst was loaded onto the bismuth vanadate electrode formed a CoF16Pc/BiVO₄ photoanode.Photoelectrochemical tests were performed in a 0.1 M phosphate buffer solution.The results showed that the CoF16Pc catalyst has good catalytic performance for water oxidation.In the same way,the CoF16Pc catalyst was loaded onto multi-walled carbon nanotubes?MWCNTs?as a cathode instead of precious metal platinum.to compose a two-electrode system of photoelectrochemical cell with CoF16Pc/BiVO₄ photoanode,which to promotes water decomposition in the photoanode and catalytic reduction of CO₂ in the cathode effectively.