Interconversion between CO₂ and HCOOH under Basic Conditions Catalyzed by PdAu Nanoparticles Supported by Amine-Functionalized Reduced Graphene Oxide as a Dual Catalyst

Recently, the utilization of formic acid (FA) or formate as promising hydrogen carriers through the interconversion between CO₂ and HCOOH or HCO₃^– and HCOO^–, respectively, has attracted increasing research interest. In this work, a PdAu bimetallic catalyst supported on phenylenediamine-alkalized reduced graphene oxide (Pd_0.50Au_0.50/PDA-rGO) was developed for catalyzing bicarbonate hydrogenation under basic conditions as well as FA/formate dehydrogenation under acidic and basic conditions. Without any additives, a very high yield (94%) of potassium formate (PF) can be achieved from the hydrogenation of potassium bicarbonate at 50 °C for 16 h. On the other hand, initial TOFs of 1.63 × 10³ and 6.98 × 10³ h^–1 were accomplished in the dehydrogenations of 6 mol/L PF and 8 mol/L FA, respectively, at 80 °C. This work successfully demonstrates highly efficient CO₂ hydrogenation and is the first report of a Pd-based heterogeneous catalyst for the additive-free dehydrogenation of concentrated (>6 mol/L) PF or FA solution. It significantly enhanced the hydrogen capacity and is of great interest for practical applications. The good performance of this catalyst is probably attributed to (i) the nanosized (1.8 ± 0.5 nm) metal particles, (ii) the presence of an amine group on the support, which can act as a proton scavenger, and (iii) the additional Au component prohibiting CO formation and enhancing the durability of the catalyst even in high concentration FA/formate solutions