Fuel cells are the most clean and efficient power source for vehicles. In particular, proton exchange membrane fuel cells (PEMFCs) are the most promising candidate for automobile applications due to their rapid start-up and low-temperature operation. Through extensive global research efforts in the latest decade, the performance of PEMFCs, including energy efficiency, volumetric and mass power density, and low temperature startup ability, have achieved significant breakthroughs. In 2014, fuel cell powered vehicles were introduced into the market by several prominent vehicle companies. However, the low durability and high cost of PEMFC systems are still the main obstacles for large-scale industrialization of this technology. The key materials and components used in PEMFCs greatly affect their durability and cost. In this review, the technical progress of key materials and components for PEMFCs has been summarized and critically discussed, including topics such as the membrane, catalyst layer, gas diffusion layer, and bipolar plate. The development of high-durability processing technologies is also introduced. Finally, this review is concluded with personal perspectives on the future research directions of this area.

Substrate-catalyzed growth offers a highly promising approach for the controlled synthesis of carbon nanostructures. However, the growth mechanisms on dynamic catalytic surfaces and the development of more general design strategies remain ongoing challenges. Here we show how an active machine-learning model effectively reveals the microscopic processes involved in substrate-catalyzed growth. Utilizing a synergistic approach of molecular dynamics and time-stamped force-biased Monte Carlo methods, augmented by the Gaussian Approximation Potential, we perform fully dynamic simulations of graphene growth on Cu(111). Our findings accurately replicate essential subprocesses–from the preferred diffusion of carbon monomer/dimer, chain or ring formations to edge-passivated Cu-aided graphene growth and bond breaks by ion impacts. Extending our simulations to carbon deposition on metal surfaces like Cu(111), Cr(110), Ti(001), and oxygen-contaminated Cu(111), our results align closely with experimental observations, providing a practical and efficient approach for designing metallic or alloy substrates to achieve desired carbon nanostructures and explore further reaction possibilities.

PEM fuel cell nowadays is expensive for widespread commercialization, though it has obvious advantages, such as high efficiency, high power density, fast startup and high system robustness. As one of the most important and costliest components in the PEM fuel cell stack, bipolar plates (BPPs) account for more than 80% of the weight and 30% of the cost of the whole stack. By replacing the conventional graphitic or machined thick metal plates with the lightweight and low-cost thin metallic sheet BPP with sustainable coating, PEM fuel cell will become an attractive choice for manufacturers. In this study, the fabrication of micro-channel features by flexible forming process (FFP) are studied first, which demonstrates the feasibility of using FFP to manufacture thin metallic BPPs. Then, the obtained knowledge is applied onto the fabrication of real thin metallic BPPs with some process amendment. The first investigation of this study focuses on the forming of micro-channel features with $100μm$ thickness stainless steel sheet. A finite element analysis (FEA) model is built and key process parameters (hardness of soft tools used in FFP, friction coefficients between contact surfaces) associated with the formability of BPPs are studied. The FEA is partly validated by the experiments. In the second investigation, finite element analysis method is adopted in the design of the BPP forming process. Based on the numerical simulation results, the die setup is prepared and some process amendments are made to improve the formability of BPPs. As a result, high quality metallic BPPs are obtained in the latter experiments, which demonstrates the feasibility to manufacture the metallic bipolar plate by FFP.

Electrically assisted forming (EAF) has been increasingly utilized as an effective auxiliary processing technology to improve the formability of hard-to-deform metals. Previous works have revealed that the phase transformation of titanium alloys subjected to electropulsing treatment (EPT) can occur at a lower temperature and in a remarkably shorter time compared with those subjected to the traditional heating treatment (THT). However, an in-depth experimental verification and further analysis is still missing so far. Therefore, to characterize the specific effects of EPT on α → β transformation process, both EPT and THT experiments were conducted on Ti–6Al–4V sheet specimens. After that, a calculation method based on the analysis of optical microscopic (OM) metallographs was developed to characterize the amount of phase transformation in EPT and THT. According to the results, it was found that the pulse current can significantly reduce the phase transus temperature and accelerate the transformation process in EPT compared with that in THT. Furthermore, the specific effects of EPT on transus temperature and phase transformation rate were investigated in detail. Based on that, the transformation kinetics of the electropulsing-induced α → β phase transformation was also analyzed using the Johnson–Mehl–Avrami model. It is revealed that the activation energies of both nucleation and growth of phase transformation are reduced by electric current. Hence, the phase transformation can start at a lower temperature and with a higher rate in EPT. The mechanism behind the effects was also discussed in detail in the present work.