constituent parameters. Among the available classes of thermoelectric materials, narrow-band gap chalcogenides [4] have shown high ZT. But these metal chalcogenides serve the purpose only in the low-temperature range. For large-scale power generation using high-grade heat, we need a material that is earth-abundant, nontoxic, and physically, chemically, and thermally stable near 1000 °C. From that perspective, oxides are promising candidates for high-temperature thermoelectric power generation. Among the bulk, n-type oxide thermoelectric materials, donor-doped SrTiO 3 (STO) have shown the best thermoelectric performance with ZT = 0.6. [5] However, ZT > 1 is a prerequisite for practical applications, which has been challenging to achieve in doped STO bulk oxides. The reasons behind their poor ZT values are their high thermal conductivity and poor electrical conductivity. It is observed that doping alone cannot improve the transport properties of STO. One must decouple the power factor (S 2 σ) and lattice thermal conductivity (κ L ) to attain high ZT values. Grain boundary engineering [6,7] and nanocompositing [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] are some of the viable routes to enhance both electron transport and induce more phonon scattering in bulk oxides.Incorporating graphite, [8,9] graphene oxide, [10] and graphene [19,22] into the donor (La, Nb)-doped STO matrix have significantly improved the ZT of STO-based bulk oxides. The most profound aspect of ZT enhancement in doped STO systems reported by various researchers is the single-crystal-like [9,19,23] electron mobility attained in these polycrystalline ceramics when they have formed composites with carbon derivatives. However, the reasons behind such huge surge in electron mobility leading to a manifold increase in electrical conductivity are yet to be fully understood. In STO-based composites with 2D graphene, enhanced electron transport is attributed to the reduction of Schottky barrier height in polycrystallinedoped STO. [11,19] However, it is debatable whether reducing the Schottky barrier alone can cause single-crystal-like electron mobility in doped STO-based composites. [23,24] Formation of the Schottky barrier is usual phenomena observed in polycrystalline materials and the presence of 2D graphene along the grain boundaries [11] is expected to facilitate the formation of excess oxygen vacancies enabling the reduction of Schottky barrier height. But that should not be specific to a particular Here, the first experimental demonstration on the effect of incorporating new generation 2D material, MXene, on the thermoelectric performance of rare-earth-free oxide perovskite is reported. The charge localization phenomenon is predominant in the electron transport of doped SrTiO 3 perovskites, which deters from achieving a higher thermoelectric power factor in these oxides. In this work, it is shown that incorporating Ti 3 C 2 T x MXene in a matrix of SrTi 0.85 Nb 0.15 O 3 (STN) facilitates the delocalization of electrons resulting in bet...

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