Development and Electrochemical Evaluation of Sustainable Algal Biochar/Hematene Aerogel Electrodes for Nitrate Conversion in Water

The development of sustainable electrode materials for electrochemical nitrate removal from water has attracted increasing interest due to the need for efficient and environmentally friendly nitrate removal technologies. This paper presents the development and electrochemical evaluation of electrodes for nitrate-associated electrocatalytic activity using sustainable materials. Algal biomass and mineral hematite, which are abundant and low-cost resources, were employed alongside hydrothermal treatment and pyrolysis, resulting in the formation of an iron-enriched hybrid aerogel with distinct structural configurations. The physicochemical properties of the prepared materials were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and electrical conductivity measurements. Their electrochemical performance was evaluated by cyclic voltammetry in sodium sulfate electrolyte containing different nitrate concentrations (0–25 mM NO3−). Electrochemical measurements demonstrated that the combination of biochar with hematene nanosheets is a promising approach for developing fully sustainable electrodes with the potential for electrochemical nitrate treatment in polluted water. Linear sweep voltammetry and scan-rate-dependent cyclic voltammetry measurements further revealed significant differences in background current and hydrogen-evolution behavior among the electrodes. These findings demonstrate that iron-doped algal biochar aerogels are promising sustainable electrodes for electrochemical nitrate treatment and support the development of low-cost, environmentally friendly water denitrification technologies.