Turning hazelnut shells into powerful catalysts for clean hydrogen production
image: Development of hazelnut shell-derived biochar to support a bifunctional MoCo electrocatalyst for HER/OER in alkaline medium
Credit: Jaime Ñanculeo, Teresa Andreu, Ignasi Sirés, Andrés Ramírez, Mara Cea, Benjamín Nahuelcura, Gerson Valenzuela, Karla Garrido-Miranda & María Eugenia González
A team of scientists in Chile and Spain has developed an innovative electrocatalyst made from hazelnut shell biochar that could lower the cost and environmental footprint of green hydrogen production. The study, published in Biochar, shows that a new molybdenum cobalt catalyst supported on nitrogen doped biochar can drive both the hydrogen evolution reaction and the oxygen evolution reaction with low overpotentials and strong long term stability in alkaline conditions.
Green hydrogen, produced through water electrolysis powered by renewable energy, is considered a key fuel for future low carbon industries and transportation. However, commercial electrolysis relies heavily on precious metals such as platinum and iridium, which are expensive and scarce. The research team set out to design a catalyst that uses abundant metals and a sustainable carbon support without compromising performance.
“We wanted to show that an agricultural residue can be transformed into a high performing material for clean energy technologies,” said María Eugenia González, senior author of the study from the University of La Frontera. “Hazelnut shells are produced in large quantities in Chile, and turning this biomass into a catalyst support creates value while reducing waste. Our goal was to demonstrate that sustainable materials can achieve excellent electrochemical activity.”
To produce the catalyst, the team first converted hazelnut shells into activated and nitrogen doped biochar using a one step treatment with potassium hydroxide and urea. This process created a highly porous carbon network with a surface area of 1102 square meters per gram and improved graphitic ordering. These structural features enhanced electron transport and provided abundant anchoring sites for metal nanoparticles.
The researchers then incorporated molybdenum and cobalt precursors into the biochar and performed a second controlled pyrolysis step. This allowed the formation of bimetallic Co6Mo6C structures and Mo2C species that served as the active catalytic phases. Microscopy and spectroscopy analyses confirmed that the metals were well dispersed within the carbon matrix and strongly bonded to nitrogen functionalities, which helped stabilize the active sites.
When tested in alkaline electrolyte, the Mo Co biochar catalyst achieved an overpotential of 0.257 volts for the hydrogen evolution reaction and 0.371 volts for the oxygen evolution reaction at a current density of 10 milliamps per square centimeter. These values approach those of conventional noble metal catalysts. The material also exhibited favorable Tafel slopes, low charge transfer resistance, and good catalytic turnover frequencies. Stability tests showed minimal performance loss over extended operation.
“This bifunctional catalyst stands out because both reactions involved in water splitting perform efficiently on the same material,” said first author Jaime Ñanculeo. “The synergy between molybdenum, cobalt, and the engineered biochar creates a strong environment for electron transfer and active site accessibility.”
The authors note that the ability to use an abundant agricultural waste product as the carbon scaffold adds significant environmental and economic value. Chile is the largest producer of hazelnuts in the Southern Hemisphere, generating large volumes of shells that are often underutilized. Converting this biomass into a functional electrocatalyst aligns with circular economy principles and reduces reliance on costly imported materials.
The team plans to scale up the synthesis process and explore the integration of the catalyst into larger electrode configurations suitable for commercial electrolyzers. They also aim to refine the metal dispersion and evaluate the catalyst under industrial operating conditions.
“This study shows that low cost, sustainable materials can play a real role in advancing hydrogen technologies,” said González. “With further optimization, biochar supported metal carbides could become a practical alternative to noble metal catalysts.”
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Journal Reference: Ñanculeo, J., Andreu, T., Sirés, I. et al. Development of hazelnut shell-derived biochar to support a bifunctional MoCo electrocatalyst for HER/OER in alkaline medium. Biochar 7, 72 (2025).
https://doi.org/10.1007/s42773-025-00464-0
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About Biochar
Biochar is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.