Development of an Autothermal Formate-Based Hydrogen Generator: From Optimization of Formate Dehydrogenation Conditions to Thermal Integration with Fuel Cells

Abstract

Formate received significant attention for storing H-2 in chemical bonds using the concept of H-2 carriers. In this report, hydrogen generation from formate was optimized systematically by varying reaction variables. Initial mass activity with a turnover frequency of 3200 mol(H2) mol(Pd)(-1) h(-1) and 92% H-2 yield were obtained in sodium formate (7 M 2.0 mL) dehydrogenation over Pd(3 wt %)/C at 80 degrees C. Influence of formate cations (Na, K, and NH4) on dehydrogenation was also elucidated, presenting that the fastest initial reaction kinetics was achieved with ammonium formate, whereas the highest H-2 yield was obtained with potassium formate (PF) in multiple catalyst recycle tests. Finally, an on-site power generation system was integrated, where a proton exchange membrane fuel cell (PEMFC) was operated in conjunction with H-2 produced from the custom developed semibatch dehydrogenation reactors. The system operation was demonstrated with continuous feeding of PF to generate H-2 and power on demand without an external heat source by utilizing waste heat produced from the PEMFC in a highly efficient manner.