Development of activated biochar from biomass-derived as a support structure to electrocatalysts synthesis for the hydrogen evolution reaction (HER)

This study explores the design of a KOH-activated biochar derived from hazelnut shells (HS) as a sustainable carbon support for the hydrogen evolution reaction (HER) in alkaline medium (1 M KOH). Biochars were synthesized at 700, 800, and 900 °C for 3 h under N 2 atmosphere and subsequently activated with KOH to promote graphitization and porosity development. Comprehensive characterization was performed using BET, SEM, Raman, XPS and XRD to evaluate surface area, morphology, and structural ordering. The AB-800 sample (800 °C, activated) exhibited the highest surface area (1253.4 m 2 g −1 ), and a moderate degree of structural ordering (I D /I G = 1.17), representing an optimal balance between hierarchical porosity and graphitic domains. Electrochemical measurements using linear sweep voltammetry and electrochemical impedance spectroscopy demonstrated a significant improvement in HER activity for AB-800, with an overpotential (η 10 ) of 0.493 V, Tafel slope of 171 mV dec −1 , and a 104.89 Ω of charge transfer resistance (R ct ), compared to non-activated samples. The enhanced electrocatalytic performance was attributed to the synergistic effect between increased active surface area, amorphous to graphitic carbon transition, and efficient electron transfer. Therefore, AB-800 is emerging as a promising sustainable alternative to advanced carbon structures (graphene or carbon nanotubes) in developing supports for HER electrocatalysts, boosting the application of biomass-derived materials in sustainable energy technologies.