HDR photography isn’t only about colors. Applying a black-and-white style to an HDR photo is a wonderful way to express a different view of the image. The first thing to do according to Jim Nix is to turn the saturation to zero. Then go to the HDR Basic sliders and play with contrast, exposure, and highlights. The HDR Structure filter is helpful when you want to punch up the details. Tone curves allow you to add a silver hue for a classic black-and-white look.
Don’t be afraid of experimenting with filters to produce an impactful photo.