Valorization of Sargassum spp. biomass as a promising source of electrocatalysts for energy generation based on life cycle assessment

This work presents the development of an S-doped biocarbon electrocatalyst, designed to address environmental and economic challenges posed by the proliferation of Sargassum spp. along the shores of Quintana Roo, Mexico. The synthesis involves a two-step process: hydrothermal treatment followed by pyrolysis at 900 °C. This method produces a material with an exceptional surface area of 2142 m2g⁻1 and a high content of thiophene-type bonds (94.30 %). The unique composition of S-doped biocarbon results in superior catalytic activity for the oxygen reduction reaction, evidenced by an onset potential of 0.981 V vs Reversible Hydrogen Electrode (RHE) and a half-wave potential of 0.878 V vs RHE. Additionally, the electrocatalyst demonstrates remarkable electrochemical stability, maintaining performance with negligible mass activity loss after 5000 cycles. A significant application of S-doped biocarbon is demonstrated in a self-breathing Anion Exchange Membrane Fuel Cell (AEMFCs), achieving 76.82 % of the power density output compared to a commercial Pt electrocatalyst cathode. Furthermore, a life cycle assessment reveals that the synthesis of 1 g of S-doped biocarbon emits only 1.27 kg CO₂-eq, which is 3.84 % of the emissions attributed to Pt. Thus, S-doped biocarbon is an environmentally friendly biocarbon and a high-performing electrocatalyst for AEMFCs, positioning it as a promising alternative to Pt for green energy applications.