Comment on the differential equation of Smagala and Fawcett

It is shown that the differential equation of Smagala and Fawcett [T.G. Smagala, W.R. Fawcett, J. Electroanal. Chem. 597 (2006) 43] for an electrified interface is similar, but not equivalent, to the hypernetted chain approximation integral equation. Nonetheless, their differential equation is of interest and is an improvement over the Poisson–Boltzmann approximation of Gouy and Chapman and may lead to further improvements.