Portfolio Items in sitemap

I would like to modify the shortcode.php to include the include all published portfolio itmes as a list of projects that are live on the webpage. I have added the following code but don’t get the result:

$output .= '<div class="col-4">';	
    $output .= '<h3>'.__("Projects", "hbthemes").'</h3>';
		        	  
	$post_list = wp_get_archives('type=portfolio&limit=20&echo=0');
	if ($post_list != '') {  
		$output .= '<ul class="hb-ul-list special-list">'.$post_list.'</ul>';  
		}	  		
 $output .= '</div>';

Can you please help me with the correct code for pulling portfolio items automatically?

Regards, Thomas