Raw IV-curve and continuous-voltage measurements for current-ripple PEM electrolyser degradation study

Raw measurement and fitted-parameter data for the manuscript "Effect of current ripple frequency on the degradation of PEM electrolysers" (Journal of Power Sources). Four PEM cells were operated for 1000 h under different current-ripple conditions (PEM1 = 300 Hz, PEM2 = pure DC, PEM3 = 600 Hz, PEM4 = 1200 Hz; all 50% magnitude). Data: per-cycle IV polarisation curves (4 PEMs x 9 cycles), continuous ~1 Hz voltage time-series (4 PEMs), and fitted four-parameter model values (R_mem, alpha, i0, I_lim) with RMSE. All files are CSV, with a README describing structure, columns, units, and the PEM-to-ripple mapping.