Inducing spin polarization via Co doping in the BiVO 4 cell to enhance the built-in electric field for promotion of photocatalytic CO 2 reduction

The efficiency of CO 2 photocatalytic reduction is severely limited by inefficient separation and sluggish transfer. In this study, spin polarization was induced and built-in electric field was strengthened via Co doping in the BiVO 4 cell to boost photocatalytic CO 2 reduction. Results showed that owing to the generation of spin-polarized electrons upon Co doping, carrier separation and photocurrent production of the Co -doped BiVO 4 were enhanced. CO production during CO 2 photocatalytic reduction from the Co-BiVO 4 was 61.6 times of the BiVO 4 . Notably, application of an external magnetic field (100 mT) further boosted photocatalytic CO 2 reduction from the Co-BiVO 4 , with 68.25 folds improvement of CO production compared to pristine BiVO 4 . The existence of a built-in electric field (IEF) was demonstrated through density functional theory (DFT) simulations and kelvin probe force microscopy (KPFM). Mechanism insights could be elucidated as follows: doping of magnetic Co into the BiVO 4 resulted in increased the number of spin-polarized photo-excited carriers, and application of a magnetic field led to an augmentation of intrinsic electric field due to a dipole shift, thereby extending carrier lifetime and suppressing charges recombination. Additionally, HCOO - was a crucial intermediate in the process of CO 2 RR, and possible pathways for CO 2 reduction were proposed. This study highlights the significance of built-in electric fields and the important role of spin polarization for promotion of photocatalytic CO 2 reduction.