The constant voltage cold start of the proton exchange membrane fuel cell (PEMFC) is usually operated at a low start-voltage in order to ensure high heat generation, which can shorten the process of the PEMFC cold start. However, the effect of constant voltage cold start on the durability of PEMFC is still unclear. Thus, in this work, the PEMFC is tested repeatedly at a low start-voltage to simulate its actual operating state in the vehicle. Then, the effect of the PEMFC durability under constant voltage cold start is investigated by polarization curve, cyclic voltammetry, electrochemical impedance spectroscopy, transmission electron microscope, and ion chromatography. After the repeatedly cold start, the output performance of the PEMFC decreases significantly. According to the characterization results, the degradation mechanism of the PEMFC at the constant voltage cold start is demonstrated to be that the PEMFC start-up repeatedly at low start-voltage leads to the decomposition of membrane polymer structure and promotes the crossover of H₂. Meanwhile, the PEMFC start-up repeatedly at low start-voltage also leads to the agglomeration of catalysts, which reduces the active area of catalysts and ultimately results in the degradation of fuel cell performance. Above all, this study proves that the durability of PEMFC can be shortened by the constant voltage cold start at 0.1 V, which provides a reference for the development of the PEMFC cold start control strategy.

High-powered and modularity is the trend for fuel cell systems. Similar to the evolution from single-cylinder to multi-cylinder in conventional internal combustion engines, fuel cell systems shall also follow this developing process. Compared to single-stack fuel cell systems, multi-stack fuel cell systems (MFCS) can enhance the system maximum output power and improve the system performance. To achieve modular design and improve the performance of high-powered MFCS, a MFCS stacks allocation optimization algorithm based on genetic algorithms is proposed in this paper. First, remaining useful life (RUL) and efficiency are choosing as an integrated optimization index, the decision model for MFCS stacks allocation is developed. Then, a heavy-duty commercial vehicle was used as an example to match the vehicle power train parameters. The genetic algorithm is used to solve the global optimal stacks allocation scheme for the vehicle in a specific application scenario. The individual fitness values in the genetic algorithm are solved by the SQP algorithm. The optimized results are analyzed and beneficial conclusions are obtained. Weights of efficiency and RUL and the number of stacks has impacts on the determination of optimal stacks allocation scheme. The overall system efficiency will increase with the efficiency factor weight increase, and the overall RUL will decrease with the efficiency factor weight increase. If the focus is on improving the overall economy of the MFCS, the efficiency/RUL weights shall be taken as 1/0. Finally, the impact of different stacks allocation schemes on the efficiency and RUL of the MFCS is compared.

Highly active and cost-efficient electrocatalysts for oxygen reduction reaction (ORR) are significant for developing renewable energy conversion devices. Herein, a nanocomposite Fe/ZnS-SNC electrocatalyst with an FeS and ZnS heterojunction on N,S-codoped carbon has been fabricated via a facile one-step sulfonating of the pre-designed Zn- and Fe-organic frameworks. Benefitting from the electron transfer from FeS to adjacent ZnS at the heterointerfaces, the optimized Fe/ZnS-SNC900 catalyst exhibits excellent ORR performances, featuring the half-wave potentials of 0.94 V and 0.81 V in alkaline and acidic media, respectively, which is competitive with the commercial 20 wt.% Pt/C (0.87 and 0.76 V). The flexible Zn-air battery equipping Fe/ZnS-SNC900 affords a higher open-circuit voltage (1.45 V) and power density of 30.2 mW cm⁻². Fuel cells assembled with Fe/ZnS-SNC900 as cathodic catalysts deliver a higher power output of 388.3 and 242.8 mW cm⁻² in H₂-O₂ and -air conditions. This work proposes advanced heterostructured ORR electrocatalysts that effectively promote renewable energy conversions.

With the increasing demand for energy, proton exchange membrane fuel cell (PEMFC) is gradually being developed for high-power applications. The power output of a single fuel cell is limited, so multi-stack fuel cell systems (MFCS) are used to meet high-power demands. The performance of fuel cells is influenced by membrane water content, but since it cannot be directly measured by sensors, indirect methods are required for estimation. Although previous studies have used Luenberger observers to estimate the membrane water content of single-stack fuel cells, the air subsystem of multi-stack systems is more complex, with stronger variable coupling and nonlinearity, making single-stack methods difficult to apply directly. To address this, the study focuses on MFCS and derives membrane water content dynamics via mass conservation. A piecewise system identification approach yields state and input-output matrices near steady states. Observability is verified, and a Luenberger observer is designed for estimating membrane water content under varying power levels. Experiments show stable and accurate estimation, supporting MFCS health management and control.