“…In the existing research, there are many diagnosis methods, either for the hydrogen leakage from the hydrogen supply system or for the hydrogen leakage in the stack. As shown in Figure 1, these methods used different strategies to diagnose hydrogen leakage, mainly including environmental hydrogen concentration diagnosis [24][25][26][27][28][29][30], hydrogen pressure decay diagnosis [9,10,[32][33][34]100,[112][113][114], gas leakage diagnosis by model-based methods or data-driven methods [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]115,123], cross-current diagnosis [10,[100][101][102][103], and diagnosis by stack (or cells) output voltage [10,100,[104][105][106][107][108]…”