Combined Hydrogen and Alkane Production by Photocatalytic Decarboxylative C–C Homocoupling of Fatty Acid by Constructing a Hydrogen-Deficient Catalytic Interface

Abstract

Decarboxylation of biomass-derived fatty acids provides an important method for the production of value-added alkane fuels and chemicals. Here, selective decarboxylative C–C homocoupling of fatty acids to obtain long-chain alkanes was achieved by heterogeneous photocatalysis under mild conditions. Hydrogen was cogenerated as the potential energy source. The high selectivity for the coupling product was realized by constructing a hydrogen-deficient catalytic interface through the combined action of Ru nanoparticles supported on TiO2 and continuous N2 blow, which can inhibit the hydrogenation of alkyl radicals and enhance the C–C coupling of alkyl radicals. C2n–2 saturated alkanes (as high as 93%) and hydrogen (as high as 20.3 μmol·mL–1) are produced from bioderived C4–C12 fatty acids in high yields under mild reaction conditions (25 °C, N2 blow). Furthermore, low-value industrial fatty acid mixtures such as coconut oil and Cinnamomum camphora seed kernel oil can be directly applied in this catalytic system and selectively yield long-chain alkanes (up to 80%) in a solvent-free system. Density functional theory (DFT) calculations and various analytical methods were applied to elucidate the possible catalytic mechanism.