MoS2 nanosheets coated KNbO3 nanowires showed enhanced piezo-photocatalytic degradation of organic pollution and hydrogen production performance.

No abstract

No abstract

GeTe and (Bi,Sb) 2 Te 3 are two representative thermoelectric (TE) materials showing maximum performance at middle and low temperature, respectively. In order to achieve higher performance over the whole temperature range, their segmented one-leg TE modules are designed and fabricated by one-step spark plasma sintering (SPS). To search for contact and connect layers, the diffusion behavior of Fe, Ni, Cu, and Ti metal layers in GeTe is studied systematically. The results show that Ti with a similar linear expansivity (10.80 × 10 −6 K −1 ) to GeTe, has low contact resistance (3 µΩ cm 2 ) and thin diffusion layer (0.4 µm), and thus is an effective metallization layer for GeTe. The geometric structure of the GeTe/(Bi,Sb) 2 Te 3 segmented one-leg TE module and the ratio of GeTe to (Bi,Sb) 2 Te 3 are determined by finite element simulation method. When the GeTe height ratio is 0.66, its theoretical maximum conversion efficiency (η max ) can reach 15.9% without considering the thermal radiation and thermal/electrical contact resistance. The fabricated GeTe/(Bi,Sb) 2 Te 3 segmented one-leg TE module showed a η max up to 9.5% with a power density ≈ 7.45 mW mm −2 , which are relatively high but lower than theoretical predictions, indicating that developing segmented TE modules is an effective approach to enhance TE conversion efficiency.

Copper sulfides (Cu2–x S) have become potential thermoelectric (TE) materials because of their high element abundance, low toxicity, and high performance. A series of Cu1.8–2x Bi2x S1–3x Se3x (0 ≤ x ≤ 0.03) bulks were fabricated using mechanical alloying and spark plasma sintering. The main Cu1.8S phase was obtained in all compositions of 0 ≤ x ≤ 0.03, and marginal Cu1.96S and Cu2S phases were detected at 0.02 ≤ x ≤ 0.03, which is attributed to the volatilization of sulfur and selenium. Benefiting from the introduced extra electronics by Bi3+ doping, the carrier concentration was optimized in 2.31×1021 cm–3. Multiscale defects introduced by Bi–Se co-doping, including secondary phases, micropores, and point defects (BiCu ••, SeS ×, and VS ••), strongly scattered the phonons, leading to a drastically decreased thermal conductivity from 2.71 W m–1 K–1 for Cu1.8S at 773 K to 0.80 Wm–1 K–1 for Cu1.74Bi0.06S0.91Se0.09. A maximum ZT of 0.78 was achieved for Cu1.74Bi0.06S0.91Se0.09 at 773 K, which is 144% higher than that of Cu1.8S (0.32). The current stress test confirms that Bi doping could improve the stability of Cu1.8S by suppressing the Cu ion migration. Our work demonstrates that Bi–Se co-doping is an effective way to enhance the TE properties for Cu1.8S.