Abstract
The fundamental nature of the approach followed for the last century to generate and distribute energy is experiencing a major upheaval. Our reliance on fossil fuels must be diminished, in order to minimize the emission of greenhouse gases and thus mitigate global warming. Correspondingly, the role of electricity in the generation, distribution and utilization of energy is expected to rise. To achieve such goals our energy infrastructure must change, allowing for a more efficient exploitation of renewable energy. This can be achieved only through the development of technologies for the large-scale storage of energy. Furthermore, the electrification of ground transportation has to begin in earnest. In all cases, electrochemical energy conversion and storage (EECS) technologies such as fuel cells (FCs) and electrolyzers (ELs) are expected to play a pivotal role owing to their low environmental impact and elevated energy conversion efficiency.
There has been a recent surge in interest in anion-exchange membranes (AEMs) as the electrolyte separator in different EECS devices such as fuel cells (AEMFCs) and electrolyzers (AEM-ELs). With respect to the state of the art FCs and ECs that employ conventional acid electrolyte separators (e.g., perfluorinated systems such as NafionTM), electrocatalysis with AEMs is much more promising. Indeed, AEMFCs and AEM-ELs can reach the performance level required by applications with electrocatalysts (ECs) that do not require a high loading of platinum-group metals (PGMs). This is due to the alkaline environment at the electrodes of AEMFCs and AEM-ELs. In addition, the use of AEMs helps in mitigating performance losses caused by the crossover of certain reactants.
AMPERE proposes a coordinated, multi-pronged effort aimed at achieving a single target which consists in the development of MEAs including innovative functional materials and capable of a performance level beyond the state of the art for application in AEMFCs and AEM-ELs. The functional materials will comprise: (i) ECs capable of effectively promoting both anodic and cathodic reactions, and chiefly the rate-determining electrochemical processes bottlenecking the operation of AEMFCs and AEM-ELs (i.e., the oxygen reduction reaction, ORR, and the oxygen evolution reaction, OER, respectively); (ii) advanced AEMs; and (iii) OH- conducting ionomers, that are necessary to bind together the different components used in the fabrication of the MEA, and play a crucial role in bestowing a high performance and durability to such devices.
EC development for the ORR, HOR (Hydrogen Oxidation), OER and HER (Hydrogen Evolution) designed at maximizing the performance of MEAs will follow different synthetic strategies to push the final performance beyond the state of the art. These strategies will include: (i) a low loading of PGMs such as Pt, Pd, Rh and Ir (L-PGM); and (ii) completely “PGM-free”. In particular, ORR ECs will be based on a hierarchical support “core” covered by a carbon nitride (CN) “shell” embedding/stabilizing the active sites in “coordination nests”. OER ECs will consist of perovskite and spinel-type oxide structures. These will be based upon first row transition metals (e.g. Fe, Co, Ni, Mn) in metal or oxide form, nanostructured and combined with mixed conductive (carbon and metal oxide) catalyst supports that exploit strong metal substrate interactions SMSI to enhance activity and stability. HER and HOR ECs will be based on Ni nanoparticles supported on porous conductive carbons (Vulcan, K-black, etc.) carbon and metal oxides (e.g. CeO2).
The ECs will undergo a comprehensive physico-chemical and “ex situ” electrochemical characterization, aimed at clarifying how the chemical composition, morphology, and structure affect the electrochemical kinetics and mechanism. Several families of AEMs and ionomers will be devised in AMPERE, characterized by composition and micro/meso/nanostructures beyond the state of the art, based on either: (i) hybrid systems consisting of polymer matrices dispersing inorganic nanofillers (IFs) that bear OH- exchange functionalities; (ii) innovative anion-exchange polyelectrolytes; or (iii) micropatterned, 3D-printed membranes; (iv) commercially-available membranes chemically or physically modified to allow anion conduction. The AEMs and ionomers will be studied in detail to elucidate how the chemical composition, thermo-mechanical properties, morphology, and structure may affect their electrical response, transport properties and long-range conduction mechanisms under well-controlled environmental conditions of hydration and CO2 concentration. The “ex-situ” results will be crucial to identify the most promising ECs, AEMs, and ionomers which will be adopted to fabricate AEMFC and AEM-EL prototypes.
These prototype devices will be tested under operando conditions to determine the parameters that maximize the compatibility between the AEMs and the electrode configurations, to optimize the performance and durability and match the requirements set by high-performance applications. Emphasis will be put on studying degradation mechanisms of ECs, membranes and ionomers. The electrochemical degradation tests will be complemented by a wide suite of spectroscopic and micro-spectroscopic methods, comparing pristine samples with their counterparts, aged under practically relevant fuel-cell operating conditions. The experimental activity will be accompanied and redirected by an extensive multiscale computation and modelling effort, aiming at: i) addressing the reaction mechanisms at the membrane-electrode interface, and ii) investigating the main factors limiting device performances and stability.
The project is organized into 5 Work Packages (WPs):
WP 1 – Coordination and project management
WP 2 – Alkaline membrane development
WP 3 -Electrocatalyst development
WP 4 – Fundamental characterization of the materials (both as prepared and post-mortem)
WP 5 – Devices fabrication, operando characterization and functional tests.
The targets of AMPERE will be reached by a Consortium exploiting the complementarity of three very active and internationally-recognized Research Units (RUs): University of Milano Bicocca (UNIMIB); University of Padova (UNIPD); National Research Council (CNR), in turn including researchers from ICCOM (Firenze) and ITAE (Messina) Institutes. The overall human effort of AMPERE is 228 Person/months, 154 delivered by the Young Researchers hired on the project. The overall project cost is 2070000 Euros, 1656000 of which requested to Italian MIUR.