Hi Rui Lima,
Thanks for using Syncfusion products.
We would like to let you know that the font icons are not loaded because of you are not referred the ej.icons.css file and we are using the ej.icons.css file to show case the button, toggle button, split button with font icons in ribbon control. You can also use your own images, font icons to the button, toggle button, split button controls in the ribbon control.
We have created a sample using your code snippets with the ej.icons.css file.
The file will be in the below location.
C:\Users\labuser\AppData\Local\Syncfusion\EssentialStudio\12.4.0.24\JavaScript\samples\web\themes\ej.icons.css
Please refer the below sample.
Sample: http://www.syncfusion.com/downloads/support/directtrac/118038/Ribbon_with_font_icons1781612444.zip
Regards,
Sarath Kumar P