Electrochromism of Mesoporous Zinc Oxide/Carboxylated Viologen Electrodes

Combination of mesoporous metal oxide electrode with monolayer of adsorbed organic chromophore can be a promising strategy to achieve an energy-saving, non-emissive, non-volatile full-color electrochromic display (ECD) with a fast response. Here, we synthesized viologen molecules with one or two carboxylic acid groups as anchors, 1-(2-carboxyethyl)-1 '-methyl-4,4 '-bipyridinium (CEMV) diiodide and N,N '-bis(2-carboxyethyl)-4,4 '-bipyridinium (CE2V) dichloride, adsorbed onto low temperature processed mesoporous ZnO electrodes to evaluate their electrochromic properties by in situ spectroelectrochemical measurements. CE2V was adsorbed at 2.5 times higher concentration than CEMV. Fast and stable reversible electrochromism in two steps as white reversible arrow purple reversible arrow yellow reversible arrow and yellpw, reversible arrow purple reversible arrow yellow, with on/off response times as 3.3/0.5 s and 1.0/0.4 s, and retention of electrochromism for 85% and 70% of the initial values after 500 redox cycles were found for CE2V and CEMV, respectively. (C) 2021 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited.

Automated summary

Combining mesoporous metal oxide electrodes with adsorbed organic chromophores can result in fast, stable, reversible electrochromism, showing a two-step color change process of white-purple-yellow-yellow and yellow-purple-yellow. CE2V exhibited higher adsorption concentration compared to CEMV, with better retention of electrochromic performance after 500 redox cycles.