Cost effective reduced graphene oxide/polyaniline composite coated SSM cathode for bio-electrochemical desalination: Advancing desalination via cathodic improvement

The microbial desalination cell (MDC) has emerged as a fascinating and green desalination process. However, cathode limitation restricts its practical implementation. An efficient catalyst layer for the cathode can improve such deficiencies significantly. The study, for the first time, investigated reduced graphene oxide (rGO) and polymerized aniline (PANI) composite catalysts to improve cathodic performance in MDC. Different rGO layers were achieved on stainless steel mesh (SSM) by varying rGO concentrations, followed by fixed PANI layer deposition. The XRD, FTIR and SEM analysis confirmed the successful formation of PANI on top of rGO on SSM with the nano-fibrous structure having rGO-characteristic XRD peak at 11.7° with O–H, (-C=O), (-C-O), C = C groups. The effect of rGO was optimized by fine-tuning of rGO mass deposition on SSM. The cyclic voltammetry (CV) results have verified that PANI-rGO_1.0-SSM (1 mg/mL rGO deposition) was electrochemically the best-performing composite with the highest CV current (2.1 mA). Therefore, three PANI-rGO_1.0-SSM composite cathodes were prepared with 15, 30, and 45 deposition cycles to apply in MDC to study the desalination and bio-electrochemical performances. The 30-deposition cycle cathode showed the best improvement among desalination rates (i.e., 40.5 % higher) and internal resistance (i.e., 96 % low) compared to the controlled cathode. Cost estimation revealed that the electro-deposition is a low-cost coating method for PANI-rGO_1.0 on SSM (US $6) and is advantageous compared to the platinum coating processes. Future research should optimize rGO and PANI loading rates and coating process to achieve better cathodic improvement for PANI-rGO composite.