From the brief critical overview of such energy conversion processes as fuel cell (FC), electrolysis of water/hydrochloric acid and discharge/charge of lithium ion batteries, and corrosion process with aid of the conception of anodic and cathodic overvoltages, we derived some key unsolved/unanswered questions which are proposed as future key issues of electrochemistry which can be split into 4 thematic issues. Furthermore, 2 issues of energy conversion at "mixing entropy batteries" by reverse electrodialysis/desalination by electrodialysis and solar galvanic cell/reverse photovoltaic cell with a semiconductive organic light emission diode (OLED) are also briefly supplemented.