A, Schematic diagram of green H2-ECT therapy in vivo. B, Schematic EC processes of two acupuncture Fe electrodes system showing anodic Fe dissolution and cathodic H2 production. c-e, The H2-production polarization curves of acupuncture electrodes recorded respectively in simulated body fluid (SBF, pH=6.0) under three different voltages (C), in SBF but with different pH (5.5, 6.0, 6.5, 7.0 and 7.5) at 3 V (D), and in fresh pork (mimicking complex tumor tissue) at two pHs (6.0 and 7.4) (E). F, Dissolved amount of iron from the anode during the EC process. G, The dependence of H2 production of the system on various pHs in SBF recorded at 3 V for 10 min (n=3). H-I, The dependence of the amounts of dissolved iron and produced H2 on voltages varying from 0 to 3 V, each for 10 min duration, at the pH=6.0 and 7.4, respectively (n=3).