<p>Design and fabrication of heterojunction comprising the vanadates and g-C₃N₄ has drawn significant interests from the prospect of broader utilization of solar energy. In this context, the present work attempts the simple annealing step for the heterojunction formation between the bicrystalline BiVO₄ and g-C₃N₄. Strikingly, BiVO₄ adopted a pure monoclinic phase, which partially transformed to tetragonal polymorph upon combination with g-C₃N₄. Such an intricate ternary phase was confirmed by X-ray diffraction technique and the optical response measurements confirmed the light absorption properties in the visible region. The electrochemical impedance spectroscopy and photocurrent measurements validated the extended charge carrier lifetime for the ternary systems compared to others. The photocatalytic activity was investigated for the degradation of bromocresol green dye (BCG) and the heterojunction performance exceeded compared to their pure phase counterparts. The kinetics of BCG degradation were found to follow pseudo-first-order kinetics and fitted with Langmuir–Hinshelwood model. The radical scavenging experiments and alignment of band gap edges substantiated the formation of S-scheme heterojunction between BiVO₄/g-C₃N₄. It was proposed that the bulk recombination of charge carriers in BiVO₄ was greatly hindered due to the formation of homojunctions between the different crystal polymorphs of BiVO₄. On the other hand, interfacial charge carrier transfer process emerging from the in-built electric field between BiVO₄ and g-C₃N₄ prompted for the S-scheme charge carrier transfer pathways. The findings of the present work open an avenue for novel design of heterojunction fabrication, with combined effects of supressed charge carrier recombination and superior charge transfer pathways.</p>