The baking soda in baking powder will decompose into carbon dioxide gas when it meets water and is heated, which can help the dough expand. However, the acidic components in baking powder can neutralize the alkalinity of baking soda and slow down the production of carbon dioxide, which leads to the swelling effect of dough is not as good as that of yeast.

Therefore, it is best to use baking powder and yeast together. Yeast is a living microorganism, which can make dough swell through fermentation, and the gas produced by yeast is more stable than baking powder, which can make flour products softer.