We first investigate the cation effect on 𝜆 !" ! 44 via tuning the H-bond network of interfacial water. It is established that the alkali cations break H-bond network in the aqueous solution following the sequence of Li < Na < K < Cs using surface-enhanced infrared absorption spectroscopy (SEIRAS) in our previous work and literature reports . A similar approach was adopted to compare the H-bond network in the aqueous solution of organic cations to establish a universal trend. After collecting the background spectrum at -0.8 V with TPA, the electrolyte was switched from TPAHCO3 to TEAHCO3 and then to TMAHCO3 using a custom flow spectroelectrochemical cell 2 . The spectra collected with TEA and TPA reflect the differences from that in TPAHCO3 (blue traces, Fig. ), which are deconvoluted into three O-H stretching modes at 3560 cm -1 , 3410 cm -1 and 3200 cm -1 , attributed to weakly H-bonded (isolated), asymmetrically H-bonded and symmetrically H-bonded H2O molecules on Au, respectively (Fig. ) . The fractions of bands attributed to the three O-H stretching modes in the difference spectra and the spectrum with TPA are comparable within the uncertainty of the peak fitting procedure, suggesting that the structure of interfacial water, as well as the H-bond network structure, is almost the same with the three organic cations. In addition, difference spectra in LiHCO3 and NaHCO3 with respect to the spectrum with TMAHCO3 were collected (red traces, Fig. ). The difference spectrum between TMA and Li is very weak, suggesting that the state of interfacial water with these two cations are similar. A positive and a negative peaks appear at 3587 and 3151 cm -1 , respectively, in the spectrum of Na with respect to TMA, suggesting an increase in the presence of isolated OH. Collectively, these spectroscopic results with extensive literature results indicate that the connectivity of H-bond network structure of interfacial water follows the sequence of TPA ≈ TEA ≈ TMA ≈ Li > Na > K > Cs. If the connectivity of the Hbonding network of interfacial water plays a decisive role in determining 𝜆 !" ! 44 , its trend is expected to be either the same or opposite to that of the connectivity of H-bond network with different cations. However, no such correlation could be identified.