By tweaking the surface properties of graphene, NUS I-FIM researchers engineered a bio-anode optimised for hosting electricity-generating bacteria, offering a fresh perspective on sustainable energy amid rising global demands.
In a significant stride towards a greener future, researchers from the Institute for Functional Intelligent Materials (I-FIM) at the National University of Singapore (NUS) have unveiled a novel, graphene-based bio-anode that taps into the power of bacteria to generate electricity.
By devising a sustainable method that carefully adjusts chemical reactions, the team has successfully optimised the surface properties of graphene nano-walls. This process allowed the researchers to strike a balance between the hydrophilicity and conductivity of the material, enhancing its biocompatibility. As a result, the graphene structures seamlessly integrated with the electricity-generating Shawanella Oneidensis MR-1 bacteria, producing a consistent bio-current.
This breakthrough, reported in the journal Carbon, represents a leap forward in the advancement of bio-electrochemical systems, opening doors to a panoply of renewable energy applications in our increasingly energy-hungry world.
Striking an electrifying balance
Bio-electrochemical systems, including microbial fuel cells, leverage the innate ability of certain microorganisms such as bacteria to transfer electrons, converting electrical energy to chemical forms and vice versa. Within these microbial fuel cells, bacteria generate electricity by breaking down organic substances, such as biowastes. From producing electricity during wastewater treatment to powering remote devices such as sensors and environmental monitoring equipment, microbial fuel cells have the potential to be a major source of renewable energy, transforming a broad range of organic wastes to electricity.
The real magic happens at the bacteria/electrode interface. It’s at this junction where electrons move from the bacteria to the electrode, leading to electricity generation in an external circuit. However, ensuring efficient electron transfer at this interface is crucial. Without optimal transfer rates, the system’s performance can be compromised. Historically, achieving this efficient electron transfer has posed challenges, with many junctions proving inconsistent or too slow for practical applications.
Graphene, often hailed as today’s “wonder material”, is a single layer of carbon atoms known for its high electrical conductivity and unique two-dimensional structure. These properties make it an ideal candidate for crafting advanced bio-anodes in microbial fuel cells. “However, marrying graphene with bio-interfaces is no simple feat,” said Professor Kostya Novoselov, Director of NUS I-FIM and co-corresponding author of the study. “Its surface isn’t naturally hospitable to living organisms, such as the Shawanella Oneidensis MR-1 bacteria, which curtails its potential in microbial fuel cells.”
The team’s research addresses this challenge head-on. Associate Professor Daria Andreeva, a principal investigator at NUS I-FIM and the second corresponding author of the study, shed light on the team’s unique approach. “We introduced a sustainable chemical control method, a novel approach that allowed us to fine-tune the surface characteristics of the graphene nano-walls comprising the bio-anode,” Assoc Prof Andreeva elaborated. “Through a careful balance of oxidation and reduction reactions, we achieved a sweet spot—where the bio-anode effectively attracts water (hydrophilicity) while retaining its electrical conductivity.”
This hydrophilicity is crucial: it enhances bacterial adhesion to the graphene, ensuring optimal microbial activity and unlocking the full potential of the bacteria for renewable energy generation.
“In a matter of hours, our bio-anode begins to generate a consistent electrical current, driven by the bacteria’s metabolic processes, resulting in a stable and reliable energy output,” said , the first author of the study and a PhD student at NUS I-FIM. “In contrast, conventional polymer-based technologies often require several days to fully synchronise with the microorganisms and reach maximum steady-state current.”
Enlisting microscopic critters for a greener world
By leveraging the unique properties of graphene in conjunction with biological processes, this study sets the groundwork for new energy-centric industries. It also empowers nascent start-ups with advanced methodologies to spearhead new applications and solutions in the energy domain.
The researchers are now setting their sights on further refining the biocompatibility of graphene in microbial fuel cells. While microbial fuel cells present challenges such as lower power output compared to conventional energy sources, the need to optimise and maintain the microbial community, and the selection of suitable electrode materials, ongoing research aims to boost their efficiency. This would broaden their practical use in both energy generation and environmental management.
Furthermore, the team is keen on delving into the compatibility of different bacterial strains with graphene-based energy devices, crafting a versatile platform capable of accommodating diverse environmental biomass. “Our goal is to transform biomass into a dependable, cost-effective energy source that is consistent and accessible, regardless of environmental variations,” added Prof Novoselov.
All three researchers mentioned are affiliated with the Department of Materials Science and Engineering, NUS.