Microbial Desalination Cell (MDC) is a promising bio-electrochemical system (BES) for desalination while treating wastewater with minimal energy consumption. However, the poor performance due to cathodic limitation hinders their large-scale application. The cathodic reduction reaction is an electrochemical surface phenomenon; thereby, the cathode's surface charge transfer and thermodynamic efficiency are crucial for reaction kinetics. To improve the cathodic reaction kinetics, the study investigated on Bismuth oxychloride (BiOCl), which is an earth-abundant, nontoxic, anti-corrosive light-responsive electro-catalyst hybridized with a very promising graphitic-C3N4 (GCN), a graphene-like electronic structured catalyst coated on stainless steel mesh (SSM) support for MDC cathode. Several photo electrocatalysts of BiOCl/GCN were prepared from different compositions of BiOCl to GCN. All the combinations of the prepared photo-electrocatalysts were characterized to understand surface morphology via FTIR, XRD, and Photo luminance-spectroscopy (PL-spectra) and for electrochemical activity via cyclic voltammetry (CV). FTIR and XRD spectroscopies confirm the successful synthesis of the BiOCl/GCN composites by adhering to distinct properties of BiOCl and GCN. PL spectra analysis revealed the effectiveness of BiOCl/GCN composites in reducing the recombination effect of photocarriers in comparison to the blank BiOCl and GCN. To understand the electrochemical performance of BiOCl/GCN composites with/without activated carbon, CV analyses with different loading rates (i.e., 20, 30, and 50 mg/cm2 ) were performed in the presence/absence of light. The 40 mg/cm2 loaded and AC supported heterojunctions exhibited higher redox current densities, revealing the effectiveness of AC as conductive support material. BiOCl/GCN (100:0 wt.%), BiOCl/GCN (75:25 wt.%) & BiOCl/GCN (25:75 wt.%) were the best three performing hybrids. However, the catalysts performed similarly in the absence and presence of light. These results contrast with the morphological analysis that confirmed the photocatalytic structure of BiOCl/GCN. These findings may be attributed to the type of light source, which demands further characterization studies. The research will eventually aid in understanding the potential applications of such promising composites for advanced electrochemical applications, including renewable energy recovery, electrochemical desalination, photovoltaic energy, and much more.