Can platypuses communicate via electroreception?
Electrocommunication is used by weakly electric fish only and it is limited to aquatic environments where the electrical conductivity of the medium allows to transmit electric signals. The best studied fish species that use this communication method are The African Mormyriformes (which comprise the Mormyridae or elephantfish and the Gymnarchidae with Gymnarchus niloticus as the only species) and the South American Gymnotiformes (or Neotropical knifefish).[1] 

The mammals that are capable of electroreception use it for passive electrolocation which means locating the prey by detecting the weak electric fields of the prey with electroreceptors. These mammals are the three living species of monotreme; the Australian duck-billed platypus (Ornithorhynchus anatinus), the Australian short-beaked echidna (Tachyglossus aculeatus) and the Western long-beaked echidna (Zaglossus bruijnii) of New Guinea; and more recently discovered, the Guiana dolphin (Sotalia guianensis) from the cetacean order.[2][3]

Note: Electroreception was reported in star-nosed mole, Condylura cristata, based on limited behavioral data (Gould et al., 1993) but the theory remains unexplained physiologically.[4]

The electrosensory system of platypus (and probably other mammals) is evolved independently and the electroreceptors belong to the trigeminal system. The physiology of the electosensory system of mammals reveal why they can't use their electroreception for conspecific communication.


  In African mormyriform and South American gymnotiform fishes this sense has evolved to an additional active system using an electric organ as a source for a.c. impedance measurement of the environment and for communication. All electroreceptors found in fishes and amphibians that do not have electric organs are of the ampullary receptor type and probably form part of the acoustico-lateralis system. In contrast, the electroreceptors in platypus belong to the trigeminal system. Their sensitivity to d.c. as well as to high-frequency pulses [2] contrasts with the mostly d.c. or lowfrequency responsiveness of ampullary receptors, which are less well-adapted to detect rapid muscle action potentials.
  
  Langner, Gerald &amp; Scheich, Henning. (2009). Electric Senses in Monotremes: Electroreception and Electrolocation in the Platypus and the Echidna. 1056-1060. 10.1007/978-3-540-29678-2_2919. 
  https://www.researchgate.net/publication/299656487_Electric_Senses_in_Monotremes_Electroreception_and_Electrolocation_in_the_Platypus_and_the_Echidna




References:

1. Map of Life - "Electrolocation and electrocommunication in weakly electric fish"
http://www.mapoflife.org/topics/topic_578_electrolocation-and-electrocommunication-in-weakly-electric-fish/ 
January 24, 2018

2. Passive electroreception in aquatic mammals. 
Czech-Damal NU, Dehnhardt G, Manger P, Hanke W. 
https://www.ncbi.nlm.nih.gov/pubmed/23187861

3. Electroreception in the Guiana dolphin (Sotalia guianensis) 
Nicole U. Czech-Damal, Alexander Liebschner, Lars Miersch, Gertrud Klauer, Frederike D. Hanke, Christopher Marshall, Guido Dehnhardt, and Wolf Hanke 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248726/

4. Edwin Gould, William McShea, Theodore Grand; Function of the Star in the Star-Nosed Mole, Condylura cristata, Journal of Mammalogy, Volume 74, Issue 1, 19 February 1993, Pages 108–116, https://doi.org/10.2307/1381909



Further reading:


1. Electroreception (edited by Theodore Holmes Bullock, Carl D. Hopkins, Richard R. Fay)



2. Neurobiology of Monotremes: Brain Evolution in Our Distant Mammalian Cousins
(edited by Ken Ashwell)



3. Sensory receptors in monotremes ( Proske U, Gregory JE, Iggo A.)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1692308/



4. Electroreception in monotremes (John D. Pettigrew) 
https://jeb.biologists.org:2083/content/jexbio/202/10/1447.full.pdf



5. Perceiving in Depth, Volume 3: Other Mechanisms of Depth Perception (By Ian P. Howard)



6. Electroreception and Electrogenesis (James S. Albert and William G.R. Crampton) http://www.ucs.louisiana.edu/~jxa4003/Albert%20PDF%27s/Albert-Crampton-Electroreception-proofs.pdf