Poisson-Boltzmann formulary: Second edition

The Poisson-Boltzmann (PB) equation provides a mean-field theory of electrolyte solutions at interfaces and in confinement, with numerous applications ranging from colloid science to nanofluidics. This formulary gathers important formulas for the PB description of a Z:Z electrolyte solution inside slit and cylindrical channels. Different approximated solutions (thin electrical double layers, no co-ion, Debye-H\"uckel, and homogeneous/parabolic potential limits) and their range of validity are discussed, together with the full solution for the slit channel. In addition, different boundary conditions are presented, the limits of the PB framework are briefly discussed, and Python scripts to solve the PB equation numerically are provided.