Activated biochar derived from agricultural and aquatic waste biomass supported on stainless steel mesh for sustainable hydrogen evolution reaction in neutral media

This research presents a sustainable and metal-free method for creating activated biochar from agricultural and aquatic waste biomass, using stainless steel mesh as support. The goal is to enhance the hydrogen evolution reaction (HER) in neutral electrolytes, a process limited by sluggish kinetics due to low proton availability and slow water dissociation. Researchers examined biochar derived from orange peel, banana peel, rice straw, corn cob, and water hyacinth.

Activated biochar from rice straw, water hyacinth, and corn cob showed improved HER performance, requiring lower overpotentials (432-436 mV) to achieve a current density of 10 mA cm⁻² compared to other materials. This enhancement is attributed to increased porosity, layered carbon morphology, intrinsic heteroatoms and mineral phases, improved electrochemically active surface area, and reduced charge-transfer resistance.

The Tafel slope, a measure of reaction kinetics, was significantly lower for these materials (323.2-352.4 mV dec⁻¹) than for other biochar-based catalysts (533.5 mV dec⁻¹) and a commercial activated carbon control (651.67 mV dec⁻¹).

The study emphasizes the need for a systematic comparison of biomass-derived carbon materials under unified conditions to establish clear relationships between precursor composition, structure, and performance. While acidic and alkaline HER studies are well-researched, neutral electrolyte conditions are less understood and more relevant to practical applications such as biological systems, wastewater treatment, and microbial electrolysis cells.

The findings contribute to the development of sustainable, cost-effective hydrogen production technologies by addressing the challenges of HER in neutral electrolytes using environmentally friendly waste materials.