Catalysts capable of efficiently interconverting electrical energy and fuels will be important for a flexible and sustainable energy supply in the future. This will require an understanding of the contributions of both the first and second coordination spheres of these catalysts to fundamental hydride and proton transfer steps occurring during the catalytic cycle. Thermodynamic models are being developed for transition metal hydride complexes of the type [HM(diphosphine)2]n (n = 0 for Co, Rh; n = +1, Ni, Pd, Pt) that allow the solution bond dissociation free energies of these and the corresponding dihydride complexes to be predicted. Examples in which this information can be used to guide the design of catalysts for H2 oxidation/production, hydrogen storage, and CO2 reduction will be given. This thermodynamic information also provides an important starting point for the rational design of proton relays incorporated in the second coordination sphere.