I've tried a few different variations and none of them seem to be working.
Specs:
Mojarra 2.2.5
Primefaces 6.0
JSF 2.2
1.) Passthrough
xmlns:h="http://java.sun.com/jsf/html"
xmlns:ps="http://java.sun.com/jsf/passthrough"
....
<h:inputText id="sign_in_useremail" type="text" class="form-control" ps:placeholder="useremail" />
2.) PassThroughAttribute
xmlns:h="http://java.sun.com/jsf/html"
xmlns:pc="http://xmlns.jcp.org/jsf/core"
...
<h:inputText id="sign_in_useremail" type="text" class="form-control"">
<pc:passThroughAttribute name="sign_in_useremail" value="useemail" />
</h:inputText>
3.) Long shot with just a label
<h:inputText id="sign_in_useremail" type="text" class="form-control" label="useremail">