It seems you're new to hybrid apps, so a little introduction might help: Icenium uses Apache Cordova
To get back to your question, there are not payment gateways exposed in Cordova by default, but respective Cordova plugins have been created. This means that you could add these plugins to your Icenium application, make the appropriate configurations and be able to use it. There is PayPal plugin for both iOS and Android:
I highly recommend going through the Working with Custom Plugins
documentation to understand how to integrate those plugins to your app.
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