High Performance H₂−Mn Regenerative Fuel Cells through an Improved Positive Electrode Morphology

The effective scaling-up of redox flow batteries (RFBs) can be facilitated upon lowering the capital costs. The application of ubiquitous manganese along with hydrogen (known as H2−Mn regenerative fuel cells (RFC)) is seen as an effective solution for this purpose. Here, we aim to evaluate different positive electrodes so as to improve the key performance metrics of the H2/Mn RFC, namely electrolyte utilization, energy efficiency, and peak power densities. Commercially available carbon paper and graphite felt are used to show that the latter provides better key performance indicators (KPIs), which is consistent with the results reported for standard all-vanadium RFBs in the literature. Even better KPIs are obtained when an in-house carbon catalyst layer (CCL) is employed in combination with graphite felt electrodes (e.g., more than 80% energy efficiency, >0.5 W cm−2 peak power density and electrolyte utilization of 20 Ah L−1 for felt and carbon metal fabric (CMF), prepared by means of electrospinning and carbonization, in comparison with about 75% energy efficiency 0.45 W cm−2 peak power density and 11 Ah L−1 electrolyte utilization for felt on its own). It is envisaged that if the electrochemical performance of CCLs can be optimized then it could open up new opportunities for the commercial exploitation of H2−Mn systems

High Performance H2−Mn Regenerative Fuel Cells through an Improved Positive Electrode Morphology

The effective scaling-up of redox flow batteries (RFBs) can be facilitated upon lowering the capital costs. The application of ubiquitous manganese along with hydrogen (known as H2−Mn regenerative fuel cells (RFC)) is seen as an effective solution for this purpose. Here, we aim to evaluate different positive electrodes so as to improve the key performance metrics of the H2/Mn RFC, namely electrolyte utilization, energy efficiency, and peak power densities. Commercially available carbon paper and graphite felt are used to show that the latter provides better key performance indicators (KPIs), which is consistent with the results reported for standard all-vanadium RFBs in the literature. Even better KPIs are obtained when an in-house carbon catalyst layer (CCL) is employed in combination with graphite felt electrodes (e.g., more than 80% energy efficiency, >0.5 W cm−2 peak power density and electrolyte utilization of 20 Ah L−1 for felt and carbon metal fabric (CMF), prepared by means of electrospinning and carbonization, in comparison with about 75% energy efficiency 0.45 W cm−2 peak power density and 11 Ah L−1 electrolyte utilization for felt on its own). It is envisaged that if the electrochemical performance of CCLs can be optimized then it could open up new opportunities for the commercial exploitation of H2−Mn systems

Trichome-like Carbon-Metal Fabrics Made of Carbon Microfibers, Carbon Nanotubes, and Fe-Based Nanoparticles as Electrodes for Regenerative Hydrogen/Vanadium Flow Cells

Regenerative hydrogen/vanadium flow cells (RHVFCs) require electrode architectures combining electrochemical, catalytic, and mechanical properties across nano-, micro-, and milliscales. The use of current carbon-based electrodes can lead to poor electrolyte utilization, slow kinetics, and rapid electrode deterioration, resulting in suboptimal electrochemical performance and hindering RHVFC's commercial viability. To address this, we here demonstrate the application of trichome-like carbon-metal fabrics (CMFs) made of carbon microfibers, carbon nanotubes, and iron-based nanoparticles as both a catalytic layer and electrode in RHVFCs by evaluating their key figures of merit. CMFs in combination with commercial carbon cloth not only offer a high power density ∼645 mW cm-2 (∼0.82 V) but also excellent cycling performance at 150 mA cm-2, yielding nearly 100% energy efficiency and a high average discharge capacity of ∼23 Ah L-1 (∼90% electrolyte utilization). These electrochemical results together with electrode microstructural features assessed by X-ray tomography and projected cost analysis represent a step change in the design and development of tailored electrodes capable of withstanding RHVFC cycling conditions without compromising electrochemical performance

Trichome-like carbon-metal fabrics made of carbon microfibers, carbon nanotubes, and Fe-based nanoparticles as electrodes for regenerative hydrogen/vanadium flow cells

Regenerative hydrogen/vanadium flow cells (RHVFCs) require electrode architectures combining electrochemical, catalytic, and mechanical properties across nano-, micro-, and milliscales. The use of current carbon-based electrodes can lead to poor electrolyte utilization, slow kinetics, and rapid electrode deterioration, resulting in suboptimal electrochemical performance and hindering RHVFC’s commercial viability. To address this, we here demonstrate the application of trichome-like carbon-metal fabrics (CMFs) made of carbon microfibers, carbon nanotubes, and iron-based nanoparticles as both a catalytic layer and electrode in RHVFCs by evaluating their key figures of merit. CMFs in combination with commercial carbon cloth not only offer a high power density ∼645 mW cm–2 (∼0.82 V) but also excellent cycling performance at 150 mA cm–2, yielding nearly 100% energy efficiency and a high average discharge capacity of ∼23 Ah L–1 (∼90% electrolyte utilization). These electrochemical results together with electrode microstructural features assessed by X-ray tomography and projected cost analysis represent a step change in the design and development of tailored electrodes capable of withstanding RHVFC cycling conditions without compromising electrochemical performance