Limits...
Thermionic Energy Conversion Based on Graphene van der Waals Heterostructures

View Article: PubMed Central - PubMed

ABSTRACT

Seeking for thermoelectric (TE) materials with high figure of merit (or ZT), which can directly converts low-grade wasted heat (400 to 500 K) into electricity, has been a big challenge. Inspired by the concept of multilayer thermionic devices, we propose and design a solid-state thermionic devices (as a power generator or a refrigerator) in using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500 K. The vdW heterostructure is composed of suitable multiple layers of transition metal dichalcogenides (TMDs), such as MoS2, MoSe2, WS2 and WSe2. From our calculations, WSe2 and MoSe2 are identified as two ideal TMDs (using the reported experimental material’s properties), which can harvest waste heat at 400 K with efficiencies about 7% to 8%. To our best knowledge, this design is the first in combining the advantages of graphene electrodes and TMDs to function as a thermionic-based device.

No MeSH data available.


The power generation efficiency ηg as a function of barrier height ϕ′ at Tc = 300 K for Th = 400 K (solid lines) and 500 K (dashed lines) from TR [K] = 500, 400, 300, 200, 100, 50 and 10 (according to the arrow direction).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5384245&req=5

f4: The power generation efficiency ηg as a function of barrier height ϕ′ at Tc = 300 K for Th = 400 K (solid lines) and 500 K (dashed lines) from TR [K] = 500, 400, 300, 200, 100, 50 and 10 (according to the arrow direction).

Mentions: The calculated results are plotted in Fig. 4 as a function of ϕ′ for TR = 500 K down to 10 K at a fixed Tc = 300 K for two heat sources: Th = 400 K (solid lines) and 500 K (dashed lines). At Th = 400 K, the efficiency is from about 8% to 20% for TR = 500 K down to 10 K. Assuming κ = 0.08 W/m/K and d = 89 nm, this corresponds to TR = 450 K and ηg is about 8% (with ϕ′ ≈ 0), which is comparable to or better than some of highly-efficient thermal harvesting devices, such as (a) a two-layer WSe2 TE-based device (ZT = 1.6) having a maximum efficiency of 6.5%9, (b) an electrochemical system for harvesting low-grade waste heat energy (<100 °C) with efficiency less than 8%43, and (c) a theoretical efficiency of 8% for ZT = 2.4 TE material at 400 K1. Note that the efficiency for a power generator is very sensitive to heat source temperature. When Th is increased from 400 K (solid lines) to 500 K (dash lines), the efficiency increases by a factor of about 2 as shown in Fig. 4.


Thermionic Energy Conversion Based on Graphene van der Waals Heterostructures
The power generation efficiency ηg as a function of barrier height ϕ′ at Tc = 300 K for Th = 400 K (solid lines) and 500 K (dashed lines) from TR [K] = 500, 400, 300, 200, 100, 50 and 10 (according to the arrow direction).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384245&req=5

f4: The power generation efficiency ηg as a function of barrier height ϕ′ at Tc = 300 K for Th = 400 K (solid lines) and 500 K (dashed lines) from TR [K] = 500, 400, 300, 200, 100, 50 and 10 (according to the arrow direction).
Mentions: The calculated results are plotted in Fig. 4 as a function of ϕ′ for TR = 500 K down to 10 K at a fixed Tc = 300 K for two heat sources: Th = 400 K (solid lines) and 500 K (dashed lines). At Th = 400 K, the efficiency is from about 8% to 20% for TR = 500 K down to 10 K. Assuming κ = 0.08 W/m/K and d = 89 nm, this corresponds to TR = 450 K and ηg is about 8% (with ϕ′ ≈ 0), which is comparable to or better than some of highly-efficient thermal harvesting devices, such as (a) a two-layer WSe2 TE-based device (ZT = 1.6) having a maximum efficiency of 6.5%9, (b) an electrochemical system for harvesting low-grade waste heat energy (<100 °C) with efficiency less than 8%43, and (c) a theoretical efficiency of 8% for ZT = 2.4 TE material at 400 K1. Note that the efficiency for a power generator is very sensitive to heat source temperature. When Th is increased from 400 K (solid lines) to 500 K (dash lines), the efficiency increases by a factor of about 2 as shown in Fig. 4.

View Article: PubMed Central - PubMed

ABSTRACT

Seeking for thermoelectric (TE) materials with high figure of merit (or ZT), which can directly converts low-grade wasted heat (400 to 500&thinsp;K) into electricity, has been a big challenge. Inspired by the concept of multilayer thermionic devices, we propose and design a solid-state thermionic devices (as a power generator or a refrigerator) in using van der Waals (vdW) heterostructure sandwiched between two graphene electrodes, to achieve high energy conversion efficiency in the temperature range of 400 to 500&thinsp;K. The vdW heterostructure is composed of suitable multiple layers of transition metal dichalcogenides (TMDs), such as MoS2, MoSe2, WS2 and WSe2. From our calculations, WSe2 and MoSe2 are identified as two ideal TMDs (using the reported experimental material&rsquo;s properties), which can harvest waste heat at 400&thinsp;K with efficiencies about 7% to 8%. To our best knowledge, this design is the first in combining the advantages of graphene electrodes and TMDs to function as a thermionic-based device.

No MeSH data available.