Energetics of 50 Hz Half Sine Pulsed DC alkaline water electrolysis : outperforms steady DC in the plasma regime but not in the low-voltage regime

Pulsed electrocatalysis and plasma catalysis offer promising avenues for advancing the hydrogen economy. This study evaluates half-sine pulsed DC (HSPDC) at 50 Hz, a readily available but unexplored pulse waveform, across various voltage regimes using alkaline water electrolysis (AWE) as a model system. We find that assessing the electrolyzer performance of the HSPDC against steady DC (SDC) based on RMS bias voltage and electrolyzer input power provides more consistent and reliable performance insights w.r.t. the prevalently used Peak bias voltage based one. HSPDC outperforms SDC in the plasma regime, exhibiting ∼170–230% higher energy efficiency, due to the dominance of higher plasma microenvironment contributions, as corroborated by optical emission spectroscopy (i.e. ∼210% higher electron density and ∼170% higher excitation temperature w.r.t. SDC at ∼70 watts of power input). However, in the explored low voltage normal electrolysis regime (6-26 voltsRMS), the energy efficiency of HSPDC is ∼11–28% lower.