The chemical transformation of CO2 and bicarbonates into useful products becomes increasingly impor- tant as the atmospheric CO2 level has reached 400 ppm. Here a small library of sulfonated aryl mono- phosphines and aryl diphosphines was tested as stabilizing ligands for a ruthenium catalytic precursor in aqueous-phase bicarbonate hydrogenation to formate. The reactions were monitored by high pressure NMR (HPNMR) spectroscopy which also revealed the presence of stable hydride species possibly linked to the superior activity of certain ligands. The different behaviors observed could be related to variations in air stabilities of the ligands. In some cases a pre-activation step of the catalytic precursor was necessary. The effect of such parameters on the stability and recyclability of the catalytic systems is discussed.