Pd/K/Co-oxide catalyst for water gas shift

Various Co₃ O₄ catalysts were investigated for the water gas shift (WGS) reaction for hydrogen production. Although the catalyst supporting only palladium (Pd/Co₃ O₄) showed low catalytic activity and higher selectivity to methanation, Pd/K/Co₃ O₄catalyst, with loading of potassium exceeding 0.78 wt%, showed high catalytic activity for the WGS reaction. Catalysts on which Pd and K exist closely showed high activity, as confirmed using various preparation methods. Results of XPS measurements for Pd/K/Co₃ O₄ revealed that supported potassium donated electrons to Pd and Co. The state of CO adsorption species was affected by the potassium loading, resulting in high catalytic activity for the Pd/K/Co₃ O₄ catalyst. These effects gave the Pd/K/Co₃ O₄ catalyst high catalytic activity for the WGS reaction. That reaction over Pd/K/Co₃ O₄ proceeds via surface cobalt carbonyl and then formate intermediates, as revealed by the TG and isotope exchange measurements using H₂¹⁸O and DRIFT.