Single-Redox-Couple Ionic p–n Junctions Enabled by Functional Decoupling of Thermo-responsiveness and Redox Activity

<jats:p>Ionic p–n junctions are emerging architectures for liquid-based thermo-electrochemical conversions due to the virtue of the large temperature coefficient of cells (αcell). Conventional dual-redoxcouple ionic p–n junctions, however, require two compatible redox couples to operate in a common electrolyte environment, severely limiting the materials design space. Here, we present a single-redox-couple ionic p–n junction by decoupling thermo-responsiveness from redox activity. A common p-benzoquinone/hydroquinone redox couple is combined with thermo-responsive poly(N-isopropylacrylamide-co-acrylic acid) and poly(N-isopropylacrylamide-co-1-vinylimidazole) nanoparticles. Matching the pKa of the polymers enables opposite temperature-induced pH changes within a common operating window, producing a concerted combination of p-type and n-type thermo-electrochemical responses. The resulting ionic p–n junction achieves a record-high αcell of 9.90 mV K−1 and operates as both a self-charging thermally regenerative electrochemical cycle and a dual-electrolyte electrochemical Peltier cooling. These results establish a general strategy and molecular design for single-redox-couple ionic p–n junctions.</jats:p>