Pequi Seed Biochar as Pd Nanoparticle Support for Catalytic Hydrogen Evolution from Ammonia Borane

Agribusiness plays a central role in the Brazilian economy, contributing roughly one-quarter of Brazil's total economic activity. However, it generates approximately 1 million tons of agro-industrial waste per year, often improperly disposed of, leading to environmental impacts. The valorization of this waste for biochar production represents a sustainable alternative. In this work, biochar derived from pequi seeds, an abundant residue from the Brazilian Cerrado, was evaluated as a support for palladium nanoparticles for the synthesis of a catalyst applied to catalytic hydrogen evolution via ammonia borane (NH₃BH₃) hydrolysis. The biochar was activated with ZnCl₂ (BCZ) and produced by pyrolysis, exhibiting a high surface area (1577.8 m² g^-1) and high porosity, characteristics favorable for metal dispersion. Transmission electron microscopy revealed a homogeneous distribution of nanoparticles, and isotopic analysis in D₂O indicated a primary kinetic isotope effect (KIE = 6.41), suggesting that water O-H bond cleavage is the rate-determining step of the reaction. The Pd catalyst exhibited a high Turnover Frequency (TOF, 90 min^-1 at 50 °C) and excellent stability over 20 cycles. These results demonstrate the potential of pequi-derived biochar as a sustainable and low-cost support for clean hydrogen production.