EIS parameters and inhibition efficiencies (IE_E) of PD-1 and PD-2 at different concentrations in 0.5 M H₂SO₄ solution at 298 K.

Inhibitor	C (mg L−1)	R s (Ω cm2)	CPE Y0 ( × 106 Sn Ω−1 cm−2)	n	R ct (Ω cm2)	R L (Ω cm2)	IEE (%)
Blank	—	1.31	640.9	0.84	8.64	5.0 × 10−7	—
PD-1	5	1.61	557.5	0.77	25.38	1.25	66.0
	10	1.49	352.3	0.82	34.24	1.48	74.8
	20	1.34	191.1	0.83	48.67	0.17	82.2
	50	1.39	282.1	0.82	53.87	2.23	84.0
	100	1.34	191.5	0.84	63.09	2.18	86.3
PD-2	5	1.95	340.0	0.72	44.75	15.81	80.7
	10	1.83	350.0	0.75	51.74	0.02	84.2
	20	1.69	305.4	0.77	61.96	6.9 × 10−4	86.1
	50	2.71	164.9	0.81	110.5	2.49	92.2
	100	1.96	112.8	0.86	136.4	11.21	93.7