The Synthesis Of Hematite Photoanodes And The Research Of Its Photoelectrochemical Water Splitting

Photoeletrochemical?PEC?water splitting is an attractive option to harvest and convert solar energy to solve the energy crisis.And hematite is a prime photoanode candidate for this application for the theoretical calculation(about 12.5 mA?cm^-2 at 1.23V vs.RHE),which is the rare material for meeting the lowest current density of 10mA?cm^-2 at 1.23 V vs.RHE under illumination for industrial applications.However,the PEC activity of hematite has some key essential limiting factors,such as short hole diffusion distance and the huge resistance at the interface of hematite and electrolyte.Based on that,the following work was studied:?1?The intended photoanode was composed of hematite nanotubes synthesized by electrochemical anodization on A3 carbon steel,which surface was modified by L-cysteine then.The potent L-cysteine facilitated the PEC performance,because the L-cysteine acts as a surface curing agent and conductive linker to promote the hole transfer smoothly.?2?The designed photoanode was consisted of hematite thin films which surface quality can be controlled by the time during the electrodeposition.Then NiOOH is deposited on its surface by photo-electrodeposition method.The NiOOH modified sample shows an excellent PEC performance,which is caused by covering NiOOH on the surface of Fe2O3,forming the p-n heterojunction which increases the band curvature and facilitates the flux of hole transfer.?3?The effect of annealing temperature on PEC water splitting with the special hematite photoanode of one-dimensional nanorod arrays synthesized by hydrothermal method was studied.Results show that high annealing temperature can make the Sn elements from the FTO spread into iron oxide,and accelerate electronic conduction.Meanwhile,the excellent wettability caused by the high annealing temperature makes it easy for the aqueous electrolyte to access the active sites.In this paper,three different nanostructure of hematite anodes were used to shorten the charge carrier migration distance,and modified treatment was applied to lower the resistance at the interface of hematite and electrolyte,and finally,increase the PEC performance.