Nanostructured and Heterostructured 2 D 1 Materials for Thermoelectrics 2

16 The rapid development in the synthesis and device fabrication of 2D materials provides new 17 opportunities for their wide applications in fields including thermoelectric energy conversion. 18 As one important research direction, the possibly poor thermoelectric performance of the 19 pristine 2D materials can be dramatically improved with patterned nanoporous structures and/or 20 heterostructures. This article reviews the recent advancement along this direction, with 21 emphasis on both fundamental understanding and practical problems. 22