Manipulating spin polarization of titanium dioxide for efficient photocatalysis

Lun Pan,Xiang Liu,Wenbo Mi,Zheng Jiang,Ji-Jun Zou,Li Yin,Chenyu Huang,Rongrong Zhang,Songbo Wang,Xiangwen Zhang,Minhua Ai

doi:10.1038/s41467-020-14333-w

Abstract

Photocatalysis has been regarded as a promising strategy for hydrogen production and high-value-added chemicals synthesis, in which the activity of photocatalyst depends significantly on their electronic structures, however the effect of electron spin polarization has been rarely considered. Here we report a controllable method to manipulate its electron spin polarization by tuning the concentration of Ti vacancies. The characterizations confirm the emergence of spatial spin polarization among Ti-defected TiO2, which promotes the efficiency of charge separation and surface reaction via the parallel alignment of electron spin orientation. Specifically, Ti0.936O2, possessing intensive spin polarization, performs 20-fold increased photocatalytic hydrogen evolution and 8-fold increased phenol photodegradation rates, compared with stoichiometric TiO2. Notably, we further observed the positive effect of external magnetic fields on photocatalytic activity of spin-polarized TiO2, attributed to the enhanced electron-spin parallel alignment. This work may create the opportunity for tailoring the spin-dependent electronic structures in metal oxides.

Highlights

Photocatalysis has been regarded as a promising strategy for hydrogen production and highvalue-added chemicals synthesis, in which the activity of photocatalyst depends significantly on their electronic structures, the effect of electron spin polarization has been rarely considered
Will remove the surface bonding carbon and hydrogen atoms in the form of CO2 and H2O, leaving the original oxygen atoms linking with skeleton Ti atom and causing the oxygen-rich environment, which form the inherent Ti defects during the thermal assembly of Ti-O-Ti parallel lattice chains (Supplementary Fig. 1)
We expect that the concentration of metal vacancies might be tuned by adjusting the numbers of glycerol groups in glycerolates

Summary

Introduction

Photocatalysis has been regarded as a promising strategy for hydrogen production and highvalue-added chemicals synthesis, in which the activity of photocatalyst depends significantly on their electronic structures, the effect of electron spin polarization has been rarely considered. The external magnetic field has been applied to strengthen the spinrestricted water oxidation process by accelerating the parallel alignment of oxygen radicals during the formation of O–O bond[24] Both electrocatalysis and photocatalysis require rapid charge transfer and long lifetime of intermediated species for redox reactions, so the electron spin property is expected to be an intrinsic factor affecting the performance of photocatalyst. Recent researches show that semiconductors like TiO2 and ZnO with abundant metal vacancies exhibit obvious room-temperature ferromagnetism[25,26,27], suggesting the appearance of asymmetric spin-up and spin-down channels in these metal-defected oxides These photocatalysts show considerably improved activity, but the intrinsic mechanism is still unclear. This work may provide a reliable way for tailoring the spin-dependent electronic structures in metal oxides

Methods

Results

Conclusion