Development of functionalized CoOx-NiFe LDH bi-layers to improve the photoelectrochemical water oxidation property of n-Si photoanode

Abstract

Tandem of photocathode (p-type semiconductor) and photoanode (n-type semiconductor) is a promising technique for photoelectrochemical (PEC) water overall splitting. However, the sluggish PEC property of the n-type semiconductor usually slow down the whole tandem system. n-silicon is a potential candidate for high-efficiency photoanode fabrication, but it is limited by the overlarded water oxidation reaction overpotential and the low stability. This work presents a CoOx and NiFe layered double hydroxide (LDH) composite bi-layer modified n-Si photoanode that exhibits excellent PEC performance. Experimental analysis and theoretical calculation results show that the CoOx-NiFe LDH bi-layer accelerates the bulk charge transfer as well as regulates the interfacial charge transfer by a synergistic effect. The prepared n-Si-CoOx-NiFe LDH photoanode exhibits a negative onset potential of 0.95 V (vs. RHE), a photocurrent of 12.2 mA cm−2 at 1.23 V (vs. RHE) and a saturated photocurrent of 41 mA m−2. In addition, the n-Si-CoOx-NiFe LDH photoanode can keep well stability for overall water splitting with nearly 100 % faradaic efficiency. This composite CoOx/NiFe LDH modification strategy provides a promising approach to improve the PEC performance of photoanodes.