Hydrothermal Reduction of NaHCO3 into Formate with Protein-Based Biomass over Pd/γ-Al2O3 Nanocatalysts

Abstract

CO2/HCO3– reduction with a renewable reductant has a promising potential for tackling the CO2 problem, but achieving high efficiency is still a challenge. Herein, protein-based biomass as the renewable reductant is found to achieve efficient NaHCO3 reduction under hydrothermal conditions. With the Pd/γ-Al2O3 nanocatalyst, the efficiency of NaHCO3 reduction reached 49.0% with l-alanine (the model compound of protein) as the reductant, which was attributed to the superior hydrogen activation property of Pd and the enhanced adsorption of NaHCO3 on the Pd/γ-Al2O3 surface. Furthermore, the mechanism study revealed that the reductive −NH2 group in protein fulfilled NaHCO3 reduction, which was moderately oxidized to N2 (not NO2– or NO3–) as the ultimate product, indicating additional merits of amending the natural nitrogen cycle and eliminating the burden of disposing toxic nitrite/nitrate. The universality of the proposed strategy was also examined with the direct use of protein and protein-based biomass of microalgae as the reductant. With efficient NaHCO3 reduction being achieved, this strategy of NaHCO3 reduction by protein-based biomass could provide a novel and sustainable approach to CO2 conversion and also a potential method of amending the anthropogenic-imbalanced nitrogen cycle.