We demonstrated both electrochromism in an aqueous electrolyte and electrocatalytic water splitting using a single functionalized electrode under mild reaction conditions (Scheme 1). The use of electrochromism in water is advantageous for developing laminated devices in which liquid gels are used. Such gels can contain volatile organic solvents and are prone to leakage. The MAs used here have been prepared by using fully automated LBL spin-coating. The system that we use is based on two functional components: a polypyridyl iron complex (1) and a common palladium dichloride salt (Scheme 1). The combination of three pyridyl moieties of the iron complex with the palladium(II) salt results in a dense, but still porous network on fluorine-doped tin oxide (FTO)-coated glass. The coordinatively saturated iron(II) complex has excellent electrochromic properties. It is deeply colored (purple) in the ground state and becomes highly transparent in the visible region upon one-electron oxidation, because of the unfavorable metal-to-ligand charge transfer (MLCT) in the formed iron(III) complex. This one-electron redox process is reversible. The palladium entity catalyzes water splitting, generating hydrogen and oxygen without the need for sacrificial materials. The interface engineering of the FTO electrodes is a multi-step process that can be conveniently carried out using fully automated spin-coating. The assembly of the different components on the surface is fast enough that the sequential steps can be carried out without significant delay times. The MA-modified electrode operates as an anode in two distinctly different electrochemical processes that occur in water under neutral conditions. In the electrochemical water splitting cell (EWSC), water is converted to oxygen at the MA-modified anode and hydrogen is converted at a platinium cathode (Scheme 1 and Figure ). Scheme 1. (A) Molecular components used for the formation of the molecular assemblies (MAs). (B) Layer-by-Layer (LbL) spin-coating of MA1 on transparent conducting oxides (TCOs) by alternative deposition of solutions of PdCl2(PhCN)2 and the metal complex 1. (C) Electrochromic switching (0.0 V -1.0 V) or oxygen evolution (> 1.22 V) of MA1 in an aqueous electrolyte solution (pH = 6.9; 0.1M LiClO4).