Influence of Ni / NiO Ratio on the Performance of Thermoelectrochemical Waste Heat Harvester Based on Hollow Microspheres

Abstract

Technologies harvesting and converting the heat of low-temperature sources into electricity are one of the current trends in modern renewable energy. Thermoelectrochemical cells based on a nickel oxide electrode are gaining increasing popularity among researchers due to the high values of the hypothetical Seebeck coefficient. This work is devoted to the study of the reduction modes effect of hollow nickel oxide microspheres on the ratio of oxide and metal nickel forms in their structure. The paper presents the synthesis of microspheres by the pyrolysis of ultrasonic aerosols of an aqueous solution of nickel nitrate. Composition and morphology are studied by scanning electron microscopy and X-ray non-standard quantitative analysis. It was shown that the proportion of metallic nickel increases with an increase in the reduction temperature to about 375°C and then changes slightly. For microspheres, reduced at 350 °C, the main parameters of the thermoelectrochemical cell were determined. It was shown that the hypothetical Seebeck coefficient in the assembled cell system is 3.1 mV/K, and the resistance to charge transfer across the electrode-electrolyte interface was less than 1 Ohm. It confirms the applicability of these materials as electrodes for electrochemical systems and the possibility of obtaining high values of output power.