With the rapid development of world economy and the exponentially growing population, both freshwater shortages and energy crises have plagued many communities around the world. The ocean is expected to mitigate the problems because seawater desalination has shown strong vitality. Forward osmosis is becoming a potential technology of producing both clean energy and clean water due to its low energy consumption and less pollution. However, the internal concentration polarization in the support layer is the main barrier to restrict the performance of forward osmosis membrane. This paper focuses on the internal concentration polarization to introduce the materials and structure of the support layer, in particular, the optimization of traditional support layer (traditional phase inversion support layer and fabrics support layer) and the characteristics and preparation methods of the novel support layer (electrostatic spinning support layer, nanoparticles doped support layer and novel phase inversion support layer). Meanwhile, the paper prospects the development trend of support layer, so that the forward osmosis technology can further expand in different fields.

Contents
1 Introduction
2 The internal concentration polarization and membrane structure parameters of forward osmosis membranes
2.1 The internal concentration polarization
2.2 Membrane structure parameters
3 The improvement of traditional support layer structure
3.1 Phase inversion support layer
3.2 Fabrics support layer
4 The novel forward osmosis membrane support layer
4.1 Electrostatic spinning support layer
4.2 Nanoparticles doped support layer
4.3 Novel phase inversion support layer
5 Conclusion and outlook