Solid-state thermoelectrics have focused on thermal to electrical energy conversion for many decades. Nevertheless, the thermoelectric energy conversion efficiency is limited by the intrinsic coupling between material properties such as electrical conductivity and the Seebeck coefficient, which reduces its efficiency despite much progress in this field. Here, we demonstrate a simple, cost-effective platform for harvesting waste heat into electricity via thermo-electrochemical cells (or thermocells) that utilize the effect of temperature on electrochemical redox potentials (i.e., the electrochemical Seebeck effect). In our preliminary experiments, coin cell type thermocells were prepared using microstructured carbon electrodes, aqueous ferricyanide/ferrocyanide redox couple, and commercial polymer separators. The wettability of the electrodes was varied by changing the duration of reactive ion etching (RIE), which improved the power performance. The highest output power (~ 75 nW) was recorded for RIE time of 3 minutes with a load of 1 kΩ. Separately, we also tested thermocells using natural wood-derived cellulose as separator materials. The performance of our thermocells will be presented, and their ability to directly power small electronic devices will be discussed.