## 1 Introduction  
The rapid promotion of renewable and sustainable energy has advanced the development of hydrogen energy and fuel cell technologies [1, 2]. As shown in Figure 1, the installed capacity of fuel cells, including PEMFCs, direct methanol fuel cells (DMFCs), phosphoric acid fuel cells (PAFCs), solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), and alkaline fuel cells (AFCs), has grown rapidly in recent years, with annual installed capacity surpassing 2500 MW. The cost of fuel cells has decreased due to improved industrial production. As it is the power source of fuel cells, the storage f hydrogen is currently a hot research topic. In-depth research on fuel cell and hydrogen storage technologies will contribute to the development of new energy technologies. Currently, hydrogen storage technologies include high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage, organic liquid hydrogen storage, and solid-state hydrogen storage. Among them, solid-state hydrogen storage technology refersto the use of solid-state hydrogen storage materials to absorb and release hydrogen under certain temperature and pressure conditions, with high volumetric hydrogen storage density, low operating pressure, high safety performance, compactness, good reversible cycling performance, reusability, etc., but the solid metal mass is heavy, and the application scenarios have more stringent requirements. Metal hydrides were initially studied primarily as hydrogen storage materials, and in addition to the advantages that solid metal hydrogen storage brings in terms of hydrogen storage, the accompanying heat changes during hydrogenation reactions in hydrogen storage alloys make them attractive for thermal engineering applications. The thermodynamic properties of MH have been used in distributed energy systems for combined heat and power, chemical thermal storage [3], heat pumps and air conditioning [4], and MH compressors [5; 6], and their thermal coupling with fuel cells has great potential for applications. During the electrochemical reaction of PEMFCs, about 40-60% of the hydrogen energy is converted into heat and is emitted into the environment, and the hydrogen storage metal can just take advantage of the waste heat generated during the operation to release hydrogen to be supplied to the PEMFC [7]. The thermally coupled system of PEMFCs and MH storage not only economises the cost of thermal management for individual components but also improves the system efficiency and energy density by realising the cogeneration. In addition, utilising the large amount of heat released during hydrogen absorption by the MH enables a preheating process for the low-temperature cold starting of the fuel cell, which raises the fuel cell temperature above the freezing point and does not consume any additional energy [8]. On this basis, other researchers have adopted different thermal coupling methods for different types of fuel cells, metallic hydrogen storage materials, and usage scenarios, which can be classified into passive and active thermal coupling according to the controllability of the thermal coupling system [9]. Common passive thermal coupling methods include heat radiation, heat conduction, heat pipe coupled heat transfer, and phase change material coupled heat transfer. [PERSON] et al. [10] developed a mathematical model of a stack, a solid-state hydrogen storage device, and a heat pipe based on the LaNi\({}_{5}\) material, and the results showed that just 20% of the cooling load at the rated power of the stack is required to maintain the MH to ensure that the hydrogen flow rate meets the demand. Other researchers have utilised phase change materials to achieve thermal coupling [11], where the reaction heat of the hydrogen storage process is recovered by the self-driven recovery of the phase change material, saving the heat exchange unit and making the system lighter and more compact. [PERSON] et al.