Innovative biochar-based electrocatalysts from chilli plants and fruits for sustainable oxygen reduction and hydrogen evolution reactions

The rapid population growth and the subsequent energy demands have led to a surge in fossil fuel usage, resulting in unprecedented environmental challenges due to carbon emissions. Green hydrogen seems to be a promising avenue to tackle the negative effects of fossil fuels to achieve an environment-friendly and sustainable energy source. In this study, we present the development of iron and nickel-based electrocatalysts derived from biochar obtained from chilli plants and their fruits for cathodic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The biochar was produced by pyrolyzing the biomass at 600 °C and 800 °C, followed by KOH activation and functionalization with iron(II) phthalocyanine for ORR and nickel nanopowder for HER. Electrochemical tests in alkaline media (0.1 M KOH for ORR and 1 M KOH for HER) demonstrated significant electrocatalytic activity. The Plant-Fe 800 electrocatalyst achieved an onset potential of 0.97 V (vs RHE) and a half-wave potential of 0.87 V (vs RHE) for ORR with minimal peroxide yield. For HER, the Chilli-Ni 800 electrocatalyst showed an overpotential of roughly 0.41 V (vs RHE). The high performance of these biochar-based electrocatalysts can be attributed to their large surface area, effective Fe-Nx active site dispersion, and the presence of nitrogen-related defects within the carbon matrix. This study highlights the potential of using sustainable, biomass-derived materials to create efficient and cost-effective electrocatalysts, paving the way for green energy.