Copper selenides with different stoichiometric compositions were prepared via facile wet-chemistry methods and sintered-Cu2−xSe exhibited the highest ZT value at a low temperature range.

Harvesting low-grade heat by an ionic hydrogel thermoelectric generator (ITEG) into useful electricity is promising to power flexible electronics. However, the poor environmental tolerance of the ionic hydrogel limits its application. Herein, we demonstrate an ITEG with high thermoelectric properties, as well as excellent capabilities of water retention, freezing resistance, and self-regeneration. The obtained ITEG can maintain the original water content at ambient conditions (302 K, 65% relative humidity (RH)) for 7 days and keep unfreezing at a low temperature (253 K). It can even be self-regenerated and recovered to its original state after a water loss in high-temperature conditions. Furthermore, a high ionic Seebeck coefficient of 11.3 mV K–1 and an impressive power density of 167.90 mW m–2 are achieved under a temperature difference of 20 K. A high power density of 60.00 mW m–2 can also be maintained even at 258 K. After drying and regeneration, ITEG-re could even exhibit a higher ionic Seebeck coefficient of 11.8 mV K–1. Successful lighting of light-emitting diodes (LEDs) and charging of capacitors demonstrate the great potential of ITEG to provide continuous energy supply for powering flexible electronics.

The most robust consensus related to ionic‐hydrogel‐based triboelectric nanogenerator (TENG) is that the charge density at the solid interface plays a pivotal role in its output performance. However, there has been no reliable evidence of the mechanism regarding the influence of ion enrichment on TENG. Higher surface charge density at the solid interface could result in higher output performance. Herein, the ionic hydrogel is prepared through polymerization reaction of the organic monomers with LiCl as the ionic conductor. The ion migration on the hydrogel surface is regulated via tuning the temperature difference between the top and bottom sides. Upon contacting with the upper electrode, more induction charges are induced on the cation‐enriched surface of hydrogel, leading to a larger output of the TENG. At the temperature difference of 25 °C, the open‐circuit voltage and maximum output power density is increased by 77% and 166% compared with the TENG without temperature field, respectively. When the temperature of the hydrogel surface is higher than 50 °C, the output performance of TENG would decrease due to the water loss of hydrogel. This research will advance further understanding of the mechanism of thermoelectric ionic conductors in TENGs, self‐powered sensors, and wearable devices.

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Bismuth tellurides is one of the most promising thermoelectric (TE) material candidates in low-temperature application circumstances, but the n-type thermoelectric property is relatively low compared to the p-type counterpart and still needs to be improved. Herein, we incorporated different copper selenides (CuSe, Cu3Se2 and Cu2−xSe) into a Bi2Te3 matrix to create the alloy by grinding and successive sintering to enable higher thermoelectric performance. The results demonstrated that all alloys achieved n-type TE characteristics and Bi2Te3-CuSe exhibited the best Seebeck coefficient and power factor among them. Along with the low thermal conductivity, the maximum dimensionless TE figure of merit (ZT) value of 1.64 at 573 K was delivered for Bi2Te3-CuSe alloy, which is among the best reported results in the n-type Bi2Te3-based TE materials to the best of our knowledge. The improved TE properties should be related to the co-doping process of Se and Cu. Our investigation shows a new method to enhance the performance of n-type TE materials by appropriate co-doping or alloying.