Experimental validation of bulk-graphene as a thermoelectric generator

Abstract

Quest for alternate energy sources is the core of most of the research activities these days. No matter how small or large amount of energy can be produced by utilizing the non-conventional techniques and sources, every bit of innovation can reshape the future of energy. In this work, experimental analysis of the thermoelectric (TE) properties of bulk-graphene in the temperature range of (303 to 363) K is presented. Graphene powder was pressed to form a pellet which was used to fabricate the TE device. The effects of temperature on the Seebeck coefficient, electrical and thermal conductivities, and the dimensionless figure of merit (FOM) were measured. The increasing value of the Seebeck coefficient (thermopower) with temperature is indicant of the metallic behavior. Additionally, the observed thermopower (TEP) is positive, which shows that the majority charge carriers are holes and peaked to a value of 56 μV K−1 at 363 K. The thermopower of the pellet is four times larger than the previously reported values for single layer graphene (SLG) and few layer graphene (FLG). In addition to this, low values of the thermal conductivity were observed for the pellet which is one of the requirements of a good TE material. Besides this, an upward trend is observed with increasing temperature for FOM, which attains a peak value of 0.0016 at 363 K, which is almost ten times that of the previously reported values.

A Qualitative Study of Defects with Enhanced Transport Properties of Graphene Exfoliated from Gum Arabic by Rapid Sonication Method

“…The increase in the thermopower of the graphene pellet is due to the rise in the number of layers from monolayers to 3–9 layers of graphene, which causes an increase in the density of defects in the sample. [ 53 ] In our case, we found lower defect concentrations since we did not involve any harsh chemicals to exfoliate graphene, which develops defects and causes the breaking of graphene layers. The thermopower of graphene pellets is positive for all the samples, which illustrates that the dominant charge carriers are holes.…”

Ultralow Thermal Conductivity Achieved by All Carbon Nanocomposites for Thermoelectric Applications

“…Our composites are shown to have lower thermal conductivity than pristine FLG and a comparable pellet of graphene or MWCNT measured along the same plane, [ 48,49 ] with a carbon black pellet exhibiting similar levels of thermal conductivity. [ 50 ] Single layer graphene exhibits very high thermal conductivity; [ 51 ] however, several theoretical (molecular and lattice dynamics simulations) studies reveal that the addition of a few layers can significantly reduce the thermal conductivity.…”

“…In-plane [40] Suspended single layered graphene (SLG) ≈4840-5300 RT - [41] Suspended graphene ≈3000-5300 RT In-plane [42] Pyrolytic graphite ≈2000 RT In-plane -Pure pitch-bonded graphite ≈200 RT In-plane [43] FLG (n = 2-4) ≈2800-1300 RT In-plane [44] SLG 600 RT - [45] Suspended graphene ≈2600-3100 350 In-plane [43] Porous 3D-graphene networks 0.54-0.90 298-773 - [34] Graphene nanoribbon(n < 5) ≈1000-1400 RT - [46] Oxygen plasma treated defected graphene supported on substrate 36 -- [47] Graphene pellet 0.38-3.02 303-363 Parallel to the pressing direction [48] MWCNT pellet 1.60-2.25 300-923 Parallel to the pressing direction [49] Carbon black pellet ≈0.2-0. pellet which is predictably lower than the graphene sheets.…”

Thermoelectric and power generation of 2D structured pieces of graphene–nanodiamonds nanocomposite

“…The Seebeck coefficient is very low for metals (only a few mV K −1 ) and much larger for semiconductors (typically a few 100 mV K −1 ). 2,3 The potential of the material for TE applications is determined in large part by a measure of the material's dimensionless gure of merit (zT), which is expressed as S 2 sT/k where S is the Seebeck coefficient, s is electric conductivity, k is thermal conductivity, and T is the absolute temperature. 4 This gure shows that for effective thermoelectricity it is essential for the TE material to have low thermal conductivity and high electrical conductivity and Seebeck coefficient.…”

“…4 This gure shows that for effective thermoelectricity it is essential for the TE material to have low thermal conductivity and high electrical conductivity and Seebeck coefficient. 4,5 The power factor is typically optimized as a function of carrier concentration (typically around 1019 carriers per cm 3 ), through doping, to give the largest zT. 6 High mobility carriers are most desirable in order to have the highest electrical conductivity.…”