Creating electron traps in BiOBr nanosheet arrays by bulk-phase F doping to restrain carrier recombination for efficient photoelectrochemical water splitting system

Abstract

Bismuth oxide semiconductors in the field of photoelectrochemical (PEC) water splitting face the problems of narrow photo response range and fast carrier compounding. On the basis of the above problems, we used a solvothermal method to prepare BiOBr nanosheet arrays (NSAs), which have a special structure that facilitates carrier transport. Subsequently, the F element was introduced into the bulk phase of BiOBr using a simple hydrothermal method. The results show that the BiOBr-F photoelectrode exhibits excellent photoelectrocatalysis performance under light and bias voltage. The photocurrent density of the BiOBr-F photoelectrode reached 28.35 μA cm−2 at 1.23 V vs. RHE, which is 2.01 times higher than that of the pure BiOBr, while a negative shift of the onset potential of 119 mV was obtained. The optical absorption tests show that the introduction of the F element forms an impurity energy level thereby extending the optical absorption range of BiOBr. Photoluminescence tests reveal that the introduction of F element effectively restricts the electron-hole pair recombination. This is due tothe fact that the F atoms replace some of the O atoms in BiOBr to create electron traps, thus forming a large number of electron-rich regions in the structure, which in turn reduces the electron-hole pair recombination. This work provides an effective solution to reduce the recombination between carriers by creating electron traps in semiconductor materials through bulk phase doping.