Frankly, I don't think the client would have any interest in your certificate. Their interest in you is whether or not you have the experience and expertise to get their job done properly.
Once you submit a proposal, you are not able to contact the client UNLESS they respond to your submission.
Add your certifications to your profile but I highly doubt it will give you an edge over the competition. Your competency, JSS, feedback and previous experiences will help you stand out.
Can I indicate the url of my web page only when I make a proposal?
Is it possible to indicate on my website that the services are only contracted through UpWork? is there any way to redirect the visitor to UpWork?