Gradient Si-and Ti-doped FeO hierarchical homojunction photoanode for efficient solar water splitting:Effect of facile microwave-assisted growth of Si-FeOOH on Ti-FeOOH nanocorals

The construction of a homojunction is an effective approach for addressing issues such as slow charge separation and charge-transfer kinetics in photoanodes.In the present work,we designed a gradient Si-and Ti-doped Fe2O3 homojunction photoanode to improve the photoelectrochemical（PEC） performance of a Ti-doped Fe2O3 photoanode.Ti-FeOOH nanocorals were synthesized using a hydrothermal process,and Si-FeOOH was grown on Ti-FeOOH nanocorals using a rapid and facile microwaveassisted（MW） technique.By varying the MW irradiation time,the thickness of the Si/Ti:Fe2O3 photoanode was adjusted and an optimized 3-Si/Ti:Fe2O3 photoelectrode was achieved with a significantly enhanced photocurrent density(1.37 mA cm-2 at 1.23 V vs.RHE) and a cathodic shift of the onset potential（150 mV） compared with that of bare Ti-Fe2O3.This enhanced PEC performance can be ascribed to homojunction formation and Si gradient doping.The Si dopant increased the donor concentration and the formation of a homojunction improved the intrinsic built-in electric field,thereby promoting charge separation and charge transfer.Furthermore,the as-formed homojunction passivated the surfacetrapping states,consequently improving the charge transfer efficiency(60% at 1.23 VRHE) at the photoanode/electrolyte interface.These findings could pave the way for the microwave-assisted fabrication of diverse efficient homojunction photoanodes for PEC water splitting applications.