In-situ elemental reaction-regulated Ag_(2)S films enable the best thermoelectric performances

Silver sulfide thinfilm,with excellent thermoelectric properties,is few reported due to the complex and time-consuming high-temperature or high-pressure synthesis process.Here,a fast ionic conductor n-type Ag2Sfilm with good crystallinity and uniform density is prepared by sputtering metal Agfilms of different thicknesses on glass and then reacting in S precursor solution at low temperature.At 450 K,β-Ag2Sfilms can be obtained and underwent a phase transition fromα-Ag2S monoclinic,which had a significant effect on their electrical and thermal properties.The grain size of Ag2Sfilms increases with the increase offilm thickness.Before and after the phase transition,the carrier concentration and mobility cause obvious changes in the electrical properties of Ag2S.The carrier concentration of body-centered cubic phaseβ-Ag2S is about three orders of magnitude higher than that of monoclinic phaseα-Ag2S,and the mobility is also 2–3 times that of the latter.Especially,after the phase transition,the conductivity ofβ-Ag2S rises exponentially from the zero conductivity ofα-Ag2S and increases with the increase of temperature.The Ag2Sfilm shows the highestfigure of merit of 0.830.30 at 600 K from the sample with±∼1600 nm thickness,which is the highest record among Ag2S-based thermoelectric materials reported so far.

Optimizing oxygen redox kinetics of M-N-C electrocatalysts via an in-situ self-sacrifice template etching strategy

The accessibility and mass transfer between catalytic sites and substrates/intermediates are essential to a catalyst's overall performance in oxygen electrocatalysis based energy devices.Here,we present an“in-situ self-sacrifice template etching strategy”for reconstructing MOF-derived M-N-C catalysts,which introduces micro-meso-macro pores with continuous apertures in a wide range and a central hollowout structure to optimize the electrochemical oxygen redox kinetics.It is realized via one-step pyrolysis of ZIF-8 single crystal epitaxially coating on a multi-functional template of the Fe,Co co-loaded mesoporous ZnO sphere.The ZnO core is reduced during the general pyrolysis of ZIF-8 into M-N-C and acts as a pore former to etch the surrounding ZIF-8 shell into diverse channels anchoring highly exposed Fe and Co-based active sites with edge enrichment.The redesigned catalyst reveals apparent structural benefits towards enhanced oxygen redox kinetics as bifunctional cathode catalysts of rechargeable zinc-air battery compared with the primitive bulk M-N-C catalysts and the mixture of commercial Pt/C and Ir/C.The unique structure-based activity advantages,the omitted template removal step and good template compatibility during synthesis make the strategy universal for the channel engineering of electrocatalysts.

Scrutinizing the facile growth of β-Ag_(2)Se fine films

Silver selenide thin film is one of the best candidates for thermoelectric devices.In the previous report,we demonstrated that high-performanced[201]orientedβ-Ag_(2)Se thin films can be prepared by direct metal surface element reaction(DMSER)solution selenization in a really short time at room temperature.However,the underlying mechanism of the fast reaction process were not discussed in depth.Herein,based on hard soft acid base(HASB)theory and strong oxidation,we further explored the possible reaction mechanism of the in-situ growth ofβ-Ag_(2)Se thin films as the function of the reaction time.The time-dependent experimental results showed that the formation of theβ-Ag_(2)Se on elemental Ag precursor(∼690nm thick)in Se/Na_(2)S precursor solution is in a growth driven mode with no obvious orientation or growth rate selections to the elemental Ag precursors.Our investigations provide a prerequisite for the further preparation of thermoelectric materials with excellent properties.

In situ constructing(MnS/Mn_(2)SnS_4)@N,S-ACTs heterostructure with superior Na/Li-storage capabilities in half-cells and pouch full-cells

Effective design of nanoheterostructure anode with high ion/electron migration kinetics can give electrode with superior electrochemical performance.However,the design and preparation of nanoheterostructure composites with high-capacity and long cycling life in half and pouch full cells remain a big challenge.Here,a novel micro-pore MnS/Mn_(2)SnS_(4)heterostructure nanowire were in situ encapsulated into the N and S elements co-doped amorphous carbon tubes(abbreviated as(MnS/Mn_(2)SnS_(4))@N,S-ACTs)and showed superior energy storage properties in Na-/Li-ion half cells and pouch full cells.The Na-/Li-storage capabilities improvement are attribute to the strong synergistic effect between MnS/Mn_(2)SnS_(4)heterostructure and N,S-ACTs protective layer,the former induces an local built-in electric field between Mn_(2)Sn S_(4)and MnS during charging/discharging,accelerating interfacial ion/electron diffusion dynamics,the latter effective maintains the morphology and volume evolution during Na~+/Li~+charging/discharging,achieving a long-term cycling stability(e.g.,high discharge capacity of 79.2 mAh/g with the capacity retention of 79.3%can be gained after 2200 cycles at 3 C in(Mn S/Mn_(2)Sn S_(4))@N,S-ACTs//LiFePO_(4)pouch full cells;a high capacity of~34 mAh/g at 10 C can be got with a Coulombic efficiency of 100%after 1000 cycles in pouch(Mn S/Mn_(2)Sn S_(4))@N,S-ACTs//Na_(3)V_(2)(PO_(4))_(2)O_(2)F full cells.