Nickel adsorbed algae biochar based oxygen reduction reaction catalyst

Lately, the bio electrochemical systems are emerging as an efficient wastewater treatment and energy conversion technology. However, their scaling-up is considerably restrained by slow-rate of cathodic oxygen reduction reaction (ORR) or otherwise by the high cost associated with the available efficient ORR catalysts. In this investigation, a cost-effective and eco-friendly approach for synthesizing Ni based ORR catalyst utilizing biosorption property of microalgae is accomplished. The synthesised Ni adsorbed algal biochar (NAB) served as an efficient cathode catalyst for enhancing ORR in a microbial carbon-capture cell (MCC). On increasing the initial concentration of Ni²⁺ in the aqueous medium from 100 mgL^-1 to 500 mgL^-1, the biosorption capacity was found to increase from 3 mgg^-1 to 32 mgg^-1 of algae cell. The MCC operated with NAB based cathode catalyst loading of 2 mgcm-² exhibited 3.5 times higher power density (4.69 Wm^-3) as compared to the one with commercial activated carbon. A significant organic matter removal (82 %) in the anodic chamber with simultaneous algal biomass productivity in the cathodic chamber was attained by MCC with cathode loaded with 2 mgcm^-2 of NAB. Hence, this easily synthesised low-cost catalyst, out of waste stream, proved its ability to improve the performance of MCC.