Progetto comune di ricerca

Celle bio-fotoelettrochimiche per la produzione di idrogeno e il trattamento di acque reflue.

Responsabili di progetto
Gaetano Squadrito, Mohamed Mahmoud
EGITTO - ASRT - Academy of Scientific Research and Technology
CNR/ASRT biennio 2018-2019 2018-2019
Ingegneria, ICT e tecnologie per l'energia e i trasporti
Area tematica
Ingegneria, ICT e tecnologie per l'energia e i trasporti
Stato del progetto

Proposta di ricerca

Introduction: A recent technology using microbial electrochemical cells (MXCs) has been introduced to directly produce electric current or hydrogen gas (H2) from different waste streams. Despite the significant improvement of MXCs performance over the past few years, one of the main challenges facing researchers for bringing MXCs to practical applications is to achieve fast organic degradation and electron transfer kinetics so that the high cost associated (i.e., capital and O&M costs) are offset by the high-value of the generated energy. Therefore, we will aim at developing the first laboratory demonstration prototype bio-photoelectrochemical cell (Bio-PEC), which will incorporate bacterial activity with semiconductor photocatalysts for recovery of valuable products from wastewater, with special attention to agriculture and food industry residuals. This research proposal represents a proof-of-concept study to better harness solar energy for water purification and renewable energy production. Thus, this technology creates a "win-win" scenario that solves a wicked waste-management challenge, cuts cost associated with conventional waste treatment, produces renewable energy, and recovers value-added products.
Recovered products (i.e., hydrogen gas and clean water) from the proposed technological approach will directly be utilised by the industry; thus, offering maximum treatment value and zero waste. The project actions, therefore, directly addresses the circular economy challenge by looking at key-sectors of the Mediterranean economy: agriculture and food industry. The development work will be underpinned by an inter-disciplinary approach through the design, preparation, and optimization of functionalised materials, electrodes and components that are able to satisfy the requested multiple-functionalities.

Although the current wastewater treatment technologies are efficient at removing most (in)organic contaminates, it is a significant energy consumer (i.e., ~1.2 kWh per each 1 m3 of wastewater treated), which makes it expensive process in terms of O&M costs. However, the wastewater's organic content is theoretically sufficient to generate approximately 3 to 4 times more energy than is required for wastewater treatment. Thus, our society could help minimize its fossil fuel extraction and consumption through capturing part of energy from organic waste streams.
A nascent technology to extract energy and chemicals value in organic waste streams is the 'microbial electrochemical cell (MXC).' The MXC is a platform technology that can recover energy value as electric current in the mode of microbial fuel cells (MFCs); as hydrogen gas (H2) in the mode of microbial electrolysis cell (MEC); or in a variety of valuable chemicals, such as hydrogen peroxide (H2O2). The hallmark of an MXC is the ability of anode-respiring bacteria (ARB) to oxidize organic matter internally and transfer the resulting electrons beyond their outermost membranes to a solid electron acceptor i.e., the anode surface. The generated electrons from organics biodegradation in an MXC's anode are transferred to the cathode compartment through an external electric circuit, while protons are diffused simultaneously into the cathode compartment through a semi-permeable membrane to reduce a terminal electron acceptor, such as oxygen.

Different electron acceptors have been successfully employed in MXCs including oxygen, but air cathodes introduces a number of issues that are one the main objectives of research on microbial electrochemical cells.
The sluggish reduction reaction in an MXC's cathode occurs usually in an electrolyte with a neutral pH (~ 7.0), which is one of the requirement of bacterial growth in any biological system i.e., an MXC's anode. Platinum (Pt) is one of the most employed cathodic catalysts in MXC research due to its catalytic activity for oxygen reduction and hydrogen evolution. Despite its high catalytic activity, one challenge facing the researchers is to replace the expensive platinum catalyst with cheaper cathodic catalysts. Recent studies showed that the voltage loss due to the activation and concentration overpotential is more than 300 mV even with platinum as a cathodic catalyst, which represents more than 30% of the theoretical voltage produced in an MXC .
Despite the efforts to replace Pt with relatively cheap metal-based catalysts, such as nickel oxide, magnesium oxide, and molybdenum disulphide (17-20), the high cost associated with these metal catalysts replacement still hinder the scale-up of MXC technology. In order to overcome this bottleneck, Chae and his co-workers have reported on a solar-assisted MEC, in which a solar cell is externally integrated with the MEC to supply the additional energy requirement for converting organic compounds in wastewater into hydrogen. However, this integration does not change the operating fundamentals of MEC, and would increase the cost associated with material and cell fabrication.
Therefore, we propose a novel self-biased, solar-driven bio-photoelectrochemical cell (Bio-PEC) that addresses this challenge by coupling electricity-producing bacteria (or anode-respiring bacteria) with semiconductor photocatalysts for hydrogen production. This Bio-PEC (bio-photoelectrochemical cells) offers the ability to combine Visible/UV-light-adsorbing photocatalysts and microorganisms for degrading bio-recalcitrant and toxic organic compounds.The concept behind Bio-PEC is to replace metal-based catalysts with a relatively cheap semi-conductor aided by a renewable energy source (i.e., solar energy). In this innovative application, there are robust synergies between the bacterial activity in the anode chamber and photo-electrocatalysts in the cathode.

Obiettivi della ricerca

The overarching goal of this collaborative project is to develop an advanced engineered platform for energy and value-added-products recovery in these organic waste streams. Consequently, it will positively impact on the nation's environment, energy, and food systems, making them more robust against possible external shocks, such as the sudden cut-off of imports due to geopolitical unrest or natural disaster, or the long-term impacts of global climate change.

We will achieve this goal by: (1) understanding the mechanistic bases behind Visible/UV-light-induced photocatalysis, (2) optimizing the photocatalysis and biodegradation configuration to maximize conversion of recalcitrant, toxic organic compounds to less-harmful by-products, along with electric current generation, and (3) gaining a comprehensive understanding of ecological interactions among key microbial members in the MXC, which, in turn, will allow a better management of these interactions. The aim is to demonstrate that the combination of photocatalysts and anode-respiring bacteria makes the treatment of recalcitrant organic compounds and hydrogen generation much more efficient and cost-effective, while simultaneously generating a set of high-value and sustainable outputs from treated waste water.

Ultimo aggiornamento: 27/06/2022