Magnetic field weakening carrier secondary recombination in/on amorphous Co0.07Fe0.93Ox co-catalysts to boost BiVO4/Co0.07Fe0.93Ox film photoanodes for solar water splitting

Amorphous and magnetic Co 0.07 Fe 0.93 O x nanoparticles were coupled on BiVO 4 film to form BVO/CFO photoanode. • Higher water oxidation activity was achieved on BVO/CFO photoanode than BVO photoanode. • Under magnetic field the activity of BVO/CFO photoanode was improved by 29.83% that was 10 times to the improvment on BVO photoanode. • Magnetic field reduces carrier secondary recombination in/on CFO co-catalysts but not change water oxidation kinetics. Amorphous co-catalysts/BiVO 4 photoanodes could achieve high-activity solar water oxidation, but the amorphous co-catalysts usually lack selectivity for electrons/holes extraction from BiVO 4 and exist carrier secondary recombination accordingly. Herein, amorphous Co 0.07 Fe 0.93 O x nanoparticles with magnetic property were coupled on BiVO 4 film to form BiVO 4 /Co 0.07 Fe 0.93 O x (BVO/CFO) film photoanode for solar water oxidation under magnetic field. In magnetic field-free condition, the BVO/CFO film photoanode had higher solar water oxidation activity (2.380 mA/cm 2 at 1.23 V vs. RHE) than BVO film photoanode (1.205 mA/cm 2 at 1.23 V vs. RHE), due to the presence of CFO co-catalysis. Under an external magnetic field of 8 mT, the solar water oxidation activity of BVO film photoanode was increased by 2.98% through magnetic field weakening the nonradiative recombination of carrier, relative to it in magnetic field-free condition. By comparison, the activity of BVO/CFO film photoanode for solar water oxidation under same magnetic field was improved by 29.83% (2.380 mA/cm 2 to 3.090 mA/cm 2 at 1.23 V vs. RHE), which was 10 times to the improvment on BVO film photoanode. In addition, the BVO/CFO film photoanode had more stable activity during continuous solar water oxidation than BVO film photoanode under magnetic field. Mechanism investigations revealed that magnetic field can significantly reduce the carrier secondary recombination in/on amorphous magnetic CFO co-catalysts to boost BVO/CFO film photoanode for solar water oxidation, but not change the reaction kinetics obviously. Download: Download high-res image (223KB) Download: Download full-size image