Hydrogen and fuel cells are envisaged as some of the most promising technologies for decarbonizing the transportation sector. In order to avoid all safety concerns associated with the use of bottled hydrogen, its production on board is one of the best options for society. This chapter discusses the catalytic steps for clean hydrogen production and purification, as well as all successful catalytic formulations that make possible the effective feed-up of low-temperature fuel cells. The recent advances in two reactions are discussed: water gas shift (WGS), being the reaction that purifies the reforming outlets by producing more hydrogen; and the preferential CO oxidation reaction, as a possible final purification step. This chapter debates the advantages and the challenges to be confronted for both reactions, pointing to their possible future combination for on board hydrogen production.