Efficient photocatalytic carbon monoxide production from ammonia and carbon dioxide by the aid of artificial photosynthesis

Abstract

Ammonium bicarbonate (NH₄HCO₃) was generated by the absorption of carbon dioxide (CO₂) into an aqueous solution of ammonia (NH₃). NH₄HCO₃ was successfully used to achieve highly efficient photocatalytic conversion of CO₂ to carbon monoxide (CO). NH₃ and/or ammonium ions (NH₄⁺) derived from NH₄HCO₃ in aqueous solution were decomposed into nitrogen (N₂) and hydrogen (H₂). Stoichiometric amounts of the N₂ oxidation product and the CO and H₂ reduction products were generated when the photocatalytic reaction was carried out in aqueous NH₄HCO₃ solution. NH₃ and/or NH₄⁺ functioned as electron donors in the photocatalytic conversion of CO₂ to CO. A CO formation rate of 0.5 mmol h⁻¹ was obtained using 500 mg of catalyst (approximately 7500 ppm) in ambient conditions (303 K, 101.3 kPa). Our results demonstrated that NH₄HCO₃ is a novel inorganic sacrificial reagent, which can be used to increase the efficiency of photocatalytic CO production to achieve one step CO₂ capture, storage and conversion.