Samples of Bi 0.913 V 0.087 O 1.587 , Bi 0.852 V 0.148 O 1.648 and Bi 0.852 P 0.148 O 1.648 were synthesised according to the previous literature. Sample purity was confirmed by laboratory powder X-ray diffraction (XRD) carried out with a Bruker D8 Advance diffractometer using Cu Ka radiation, via