Effect of carbon material and surfactant on ink property and resulting surface cracks of fuel-cell microporous layers

Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.

Recent advances in regulating the performance of acid oxygen reduction reaction on carbon-supported non-precious metal single atom catalysts

Developing high performance and low-cost catalysts for oxygen reduction reaction(ORR)in challenging acid condition is vital for proton-exchange-membrane fuel cells(PEMFCs).Carbon-supported nonprecious metal single atom catalysts(SACs)have been identified as potential catalysts in the field.Great advance has been obtained in constructing diverse active sites of SACs for improving the performance and understanding the fundamental principles of regulating acid ORR performance.However,the ORR performance of SACs is still unsatisfactory.Importantly,microenvironment adjustment of SACs offers chance to promote the performance of acid ORR.In this review,acid ORR mechanism,attenuation mechanism and performance improvement strategies of SACs are presented.The strategies for promoting ORR activity of SACs include the adjustment of center metal and its microenvironment.The relationship of ORR performance and structure is discussed with the help of advanced experimental investigations and theoretical calculations,which will offer helpful direction for designing advanced SACs for ORR.

Structure and Control Strategies of Fuel Cell Vehicle

The structure and kinds of the fuel cell vehicle (FCV) and the mathematical model of the fuel cell processor are discussed in detail. FCV includes many parts: the fuel cell thermal and water management, fuel supply, air supply and distribution, AC motor drive, main and auxiliary power management, and overall vehicle control system. So it requires different kinds of control strategies, such as the PID method, zero-pole method, optimal control method, fuzzy control and neural network control. Along with the progress of control method, the fuel cell vehicle's stability and reliability is up-and-up. Experiment results show FCV has high energy efficiency.

A review on the sealing structure and materials of fuel-cell stacks

Proton-exchange-membrane fuel cells(PEMFCs)have the characteristics of zero emissions,a low operating temperature and high power density,and have great potential in improving energy-utilization efficiency.However,fuel cells are still quite expensive as a result of the cost of key components,including the membranes,catalysts and bipolar plates of PEMFCs.As a result of the cost and importance of these items,most researchers have focused on improving the lifetime and performance of fuel-cell stacks in recent years.In contrast,seals,sealants and adhesives play a more mundane role in the overall performance of a fuel cell,but failure of these materials can lead to reduced system efficiency,system failure and even safety issues.Little attention has been paid to the performance and durability of these products but as other fuel-cell components improve,these seals are becoming an even more critical link in the long-term performance of fuel cells.This article highlights the importance and background of fuel-cell seals.The latest research progress on the mechanical properties and structural optimization of different sealing materials is reviewed.

Engineering nanoporous and solid core-shell architectures of lowplatinum alloy catalysts for high power density PEM fuel cells

Low-platinum(Pt)alloy catalysts hold promising application in oxygen reduction reaction(ORR)electrocatalysis of protonexchange-membrane fuel cells(PEMFCs).Although significant progress has been made to boost the kinetic ORR mass activity at low current densities in liquid half-cells,little attention was paid to the performance of Pt-based catalysts in realistic PEMFCs particularly at high current densities for high power density,which remains poorly understood.In this paper,we show that,regardless of the kinetic mass activity at the low current density region,the high current density performance of the low-Pt alloy catalysts is dominantly controlled by the total Pt surface area,particularly in low-Pt-loading H_(2)–air PEMFCs.To this end,we propose two different strategies to boost the specific Pt surface area,the post-15-nm dealloyed nanoporous architecture and the sub-5-nm solid core–shell nanoparticles(NPs)through fluidic-bed synthesis,both of which bring in comparably high mass activity and high Pt surface area for large-current-density performance.At medium current density,the dealloyed porous NPs provide substantially higher H_(2)–air PEMFC performance compared to solid core–shell catalysts,despite their similar mass activity in liquid half-cells.Scanning transmission electron microscopy images combined with electron energy loss spectroscopic imaging evidence a previously unreported“semi-immersed nanoporous-Pt/ionomer”structure in contrast to a“fully-immersed core–shellPt/ionomer”structure,thus favoring O_(2) transport and improving the fuel cell performance.Our results provide new insights into the role of Pt nanostructures in concurrently optimizing the mass activity,Pt surface area and Pt/Nafion interface for high power density fuel cells.

Enhanced ORR performance of Pt catalysts in acidic media by coupling with topological C defects

Defect engineering is a promising strategy for supported catalysts to improve the catalytic activity and durability.Here,we selected the Cmatrix enriched with topological defects to serve as the substrate material,in which the topological defects can act as anchoring centers to trapPt nanoparticles for driving the O_(2) reduction reactions(ORRs).Both experimental characterizations and theoretical simulations revealed the strong Ptdefect interaction with enhanced charge transfer on the interface.Despite a low Pt loading,the supported catalyst can still achieve a remarkable 55 mV positive shift of half-wave potential toward ORR in O_(2)-saturated 0.1 M HClO_(4) electrolyte compared with the commercial Pt catalyst on graphitized C.Moreover,the degeneration after 5,000 voltage cycles was negligible.This finding indicates that the presence of strong interaction between Pt and topological C defects can not only stabilize Pt nanoparticles but also optimize the electronic structures of Pt/C catalysts toward ORR.