NiSe2-CoSe2 Nanowires for Electrochemical Charge Storage and Heat to Electricity Conversion

Abstract: The integration of thermoelectrochemical cells (TEC) with electrochemical energy storage devices represents a powerful strategy for simultaneously converting low-grade thermal energy into electricity and storing it for on-demand use. Central to this approach is the development of multifunctional electrode materials that exhibit both high electrochemical activity and strong thermoelectric response. In this work, we report the synthesis of NiSe2-CoSe2 (NCS) nanowires grown directly on activated carbon cloth (ACC), forming a robust and binder-free electrode architecture. This hybrid material (NCS/ACC) demonstrates superior performance compared to its monometallic counterparts in both electrochemical energy storage and ionic thermoelectric conversion. As an electrode for asymmetric supercapacitors (ASC), the NCS/ACC//AC/ACC device delivers a high energy density of 28 Wh kg⁻¹ at a power density of 646 W kg-1, outperforming previously reported ASC systems based on Ni and Co selenides. Additionally, in a TEC configuration using 1 M NaOH as the electrolyte, the NCS/ACC electrode exhibits a remarkable Seebeck coefficient of -3.4 mV K-1 and a thermal charge storage of -1.02 J, highlighting its dual functionality in thermal energy harvesting and storage. These results position NCS/ACC as a promising electrode for next-generation hybrid energy systems, where efficient heat-to-electricity conversion is coupled with high-performance electrochemical energy storage opening new avenues for self-powered devices and sustainable energy technologies. Keywords: Thermoelectrochemical cell (TEC); NiSe2-CoSe2 nanowires; Electrochemical Charge storage; Asymmetric Supercapacitor (ASC); Heat-to-electricity conversion PhD candidate Rupa Ranjani Palanisamy delivered this presentation at the 76th Irish Universities Chemistry Research Colloquium, held in Maynooth University between 16th and 17th June 2025.