The share market of hydrogen is increasing with the implementation of fuel cell systems and the growing demand for zero-emission fuels. Hydrogen production by using metal catalyst will need to increase with this growing market. However, some carbon is deposited on the catalyst but there was a window of operation where the deposited carbon did not have too great an effect on hydrogen production under different conditions. Carbon formation deactivates the catalyst, resulting in short life cycles. In order to improve process performance, in particular minimizing catalyst deactivation caused by carbon formation and maximizing the yield of hydrogen product, the addition of the promoters to catalyst is the most familiar method. The book is focused on the art of the promoters application on metal catalyst for hydrogen production from the methane steam reforming process at high pressure and the steam iron process over promoted Fe-oxide based catalyst.