Photocatalytic Hydrogen Production from Alcohols to In-Situ Hydrogenation of Nitrogen to Ammonia by a Dual-Catalyst System

Abstract

Haber-Bosch process to produce ammonia from hydrogenation of nitrogen is high energy intensive and non-sustainable due to substantial CO2 emissions primarily from the H2 generation. Herein, the nitrogen hydrogenation into ammonia is realized through a sustainable synthesis method by a biomimetic photocatalytic dual-catalyst system which used renewable alcohols as hydrogen source, a low redox potential H4SiW12O40 (SiW12) as photocatalyst and suspended Pt-on-carbon (Pt/C) particles as nitrogen hydrogenation catalyst. The SiW12 can quickly dehydrogenate alcohols using solar energy to produce electrons and protons. The produced electrons were stored in SiW12 anion and could be transferred by SiW12 to be released to reduce the nitrogen with protons into ammonia on the Pt/C. The synergistic effects between SiW12 and Pt can enhance electrons into [NNHn]+ and [NHn]+ species through an associative-distal pathway, resulting in the nitrogen hydrogenation with a very low activation energy, and further breaking the scaling theory relations.

Keywords: Photocatalytic reaction, Nitrogen hydrogenation, Ammonia, H2 generation