Enhanced photoelectrochemical performance and stability of Si nanowire photocathode with deposition of hematite and carbon

Abstract

Tremendous efforts have been dedicated to the development of transition metal and/or metal oxide surface coating materials to enhance the activity and stability of photoelectrodes. Nanostructured Si photoelectrodes have shown outstanding photoelectrochemical (PEC) performance due to their effective photon absorption and charge generation, separation, and mobility. While the chemical stability and surface reaction efficiency of Si photoelectrodes still need improvement before commercial application. Herein, we report the design and synthesis of a composite Si photoelectrode with a configuration of C/α-Fe2O3/Si nanowires, which presented a stable photoelectrochemical hydrogen production in neutral electrolyte. The p-Si nanowires were prepared by metal-assisted chemical etching for enhanced optical absorption and decorated with a mesoporous α-Fe2O3 thin film (∼80 nm) through pyrolysis of ferrocene. A thin carbon passivation layer (∼20 nm) was further deposited through ion sputtering further increasing the stability of the composite structure and low bias photocurrent. The role of α-Fe2O3 and carbon layer have been discussed. The composite photoelectrode shows a stable photocurrent of ∼−27 mA/cm2 in 2 h and an anodic onset potential shift of ∼0.33 V relative to the bare Si in the neutral solution.