We demonstrate that manganese (Mn) can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency via a chemical vapor deposition process. Dense and uniform SWNT films with high quality were obtained by using a Mn catalyst, as characterized by scanning electron microscopy, Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. Moreover, we found that the surface property of the substrate plays a critical role in the growth efficiency of SWNTs. By deposition of a thin oxide layer (SiO 2 or Al 2 O 3 ) on the top of a SiO 2 /Si substrate, the growth efficiency of SWNTs was dramatically improved. The successful growth of SWNTs by Mn catalyst provides new experimental information for understanding the growth mechanism of SWNTs, which may be helpful for their controllable synthesis.

Flexible thermoelectric materials and devices show great potential to solve the energy crisis but still face great challenges of high cost, complex fabrication, and tedious postprocessing. Searching for abnormal thermoelectric materials with rapid and scale-up production can significantly accelerate their applications. Here, we develop superlarge 25 × 20 cm2 commercial graphite-produced composite films in batches, achieved by a standard 10 min industrial process. The high cost effectiveness (S 2σ/cost) of 7250 μW g m–1 K–2 $–1 is absolutely ahead of that of the existing thermoelectric materials. The optimized composite film shows a high power factor of 94 μW m–1 K–2 at 150 °C, representing the optimal value of normal carbon materials so far. Furthermore, we design two types of flexible thermoelectric devices fabricated based on such a novel composite, which achieve an output open-circuit voltage of 3.70 mV using the human wrist as the heat source and 1.33 mV soaking in river water as the cold source. Our study provides distinguished inspiration to enrich flexible and cost-effective thermoelectric materials with industrial production.

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GeTe and its derivatives emerging as a promising lead-free thermoelectric candidate have received extensive attention. Here, a new route was proposed that the minimization of κL in GeTe through considerable enhancement of acoustic phonon scattering by introducing ultrafine ferroelectric domain structure. We found that Bi and Ca dopants induce strong atomic strain disturbance in the GeTe matrix because of large differences in atom radius with host elements, leading to the formation of ultrafine ferroelectric domain structure. Furthermore, large strain field and mass fluctuation induced by Bi and Ca codoping result in further reduced κL by effectively shortening the phonon relaxation time. The co-existence of ultrafine ferroelectric domain structure, large strain field, and mass fluctuation contribute to an ultralow lattice thermal conductivity of 0.48 W m–1 K–1 at 823 K. Bi and Ca codoping significantly enhances the Seebeck coefficient and power factor through reducing the energy offset between light and heavy valence bands of GeTe. The modified band structure boosts the power factor up to 47 μW cm–1 K–2 in Ge0.85Bi0.09Ca0.06Te. Ultimately, a high ZT of ∼2.2 can be attained. This work demonstrates a new design paradigm for developing high-performance thermoelectric materials.