Performance improvement of air-breathing proton exchange membrane fuel cell(PEMFC) with a condensing-tower-like curved flow field

Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In this paper, we aim to improve the air diffusion and fuel cell performance by employing a novel condensing-tower-like curved flow field rather than an additional fan, making the fuel cell more compact and has less internal power consumption. Polarization curve test and galvanostatic discharge test are carried out and proved that curved flow field can strengthen the air diffusion into the PEMFC and improve its performance. With appropriate curved flow field, the fuel cell peak power can be 55.2%higher than that of planar flow field in our study. A four-layer stack with curved cathode flow field is fabricated and has a peak power of 2.35 W(120 W/kg).

Critical importance of current collector property to the performance of flexible electrochemical power sources

Flexible electrochemical power sources are attracting increasing attentions for their unique advantages like flexibility, shape diversity, light weight and excellent mechanical properties. In this research, we discover that the current collector can dramatically affect the performance of flexible electrochemical power sources with large size. For flexible air-breathing proton exchange membrane fuel cell (PEMFC), the performance could have more than 8 times increase by only adjusting the directions of current collectors. The different performances of different current collection types are mainly attributed to the diverse lengths of the electron transfer pathways. In addition, the conductivity of current collector can dramatically affect the capability of flexible PEMFCs with large-size. The flexible PEMFCs with thicker carbon nanotube membrane as current collector (low electric resistance) show higher ability. A mathematic model is successfully built in this work to further understand the performance. Moreover, the model and simulation are also applicable to other flexible power sources, such as flexible Li-ion battery and supercapacitor.

Plasma treated carbon paper electrode greatly improves the performance of iron-hydrogen battery for low-cost energy storage

A novel iron-hydrogen battery system, whose Fe^(3+)/Fe^(2+)cathode circumvents slowly dynamic oxygen reduction reaction and anode is fed with clean and cordial hydrogen, is systematically investigated. The maximum discharge power density of the iron-hydrogen battery reaches to 96.0 m W/cm^(2) under the room temperature. The capacity reaches to 17.2 Ah/L and the coulombic and energy efficiency are achieved to99% and 86%, respectively, during the galvanostatic charge-discharge test. Moreover, stable cycling test is observed for more than 240 h and 100 cycles with the iron sulfate in the sulfuric acid solutions. It is found that air plasma treatment onto the cathode carbon paper can generate the oxygen-containing groups and increase the hydrophilic pores proportion to ca. 40%, enlarging nearly 6-fold effective diffusion coefficient and improving the mass transfer in the battery performance. The simple iron-hydrogen energy storage battery design offers us a new strategy for the large-scale energy storage and hydrogen involved economy.

Highly Distorted Platinum Nanorods for High-Efficiency Fuel Cell Catalysis

Different from studies where less defective platinum(Pt)-based nanomaterials have been widely used to improve the catalysis of the oxygen reduction reaction(ORR)for proton-exchange membrane fuel cells(PEMFCs),herein we have demonstrated that a new class of Pt nanorods(NRs)with a highly distorted configuration can be applied as an advanced,high-efficiency fuel cell catalyst,as transformed from spongy Pt–tellurium NRs(PtTe2 NRs)through sequential chemical and electrochemical aging procedures.The resulting highly distorted Pt NRs exhibit excellent ORR-specific and mass activities of 4.70mA cm−2 and 2.77 Amg−1 Pt at 0.90 V versus the reversible hydrogen electrode(RHE),which are 18.8 and 16.3 times higher than those of commercial Pt/C catalyst,and the mass activity is 6.3 times higher than 2020 U.S.Department of Energy target.Additionally,negligible activity decays were observed after 30,000 cycles.The high ORR performance endows these unique Pt NRs with enhanced activity and lifetimes for practical fuel cell catalysis in comparison with commercial Pt/C,which is consistent with the experimental results.It has been demonstrated that the anomaly of strong electron–lattice coupling suppresses Coulombic repulsion for barrier-free electron transfer while concurrently exposing a large number of active sites,which is a key to superior high-performance fuel cell reactions.