Fig. 4

Water electrolysis in different pH solutions. a HER electrocatalysis on P–Mo–N catalyst in the different pH solutions: 0.1 mM NaOH, 0.5 M Na₂SO₄, 0.05 M H₂SO₄, and 0.5 M H₂SO₄; b the electrochemical impedance spectra (EIS) of P–Mo–N sample under the four solution: 0.1 mM NaOH, 0.5 M Na₂SO₄, 0.05 M H₂SO₄, and 0.5 M H₂SO₄, the bias voltage is set to be −100 mV; c the plots of ∆j at −0.1 V vs. RHE against the scan rate, the corresponding slopes are also shown, the corresponding CV curves in the region of −0.2 ~ 0.0 V vs. RHE are given in Supplementary Figure 24. Please note that the dates of 0.5 M H₂SO₄ condition are obtained from above results, not the new dates