Highly Efficient Photocatalytic Syngas Production from Formic Acid Using Iron-Porphyrins as Catalysts Integrated with CdS/CNTs Heterojunctions under Visible Light

Syngas (H₂ + CO) is a compatible fuel for internal combustion engines, or it can be transformed to liquid fuels, which can help overcome future energy crises sustainably. In this study, we report an inexpensive and highly active photocatalytic system for production of syngas from formic acid under ambient conditions. The photocatalytic system comprising CdS/CNT hybrids and a porphyrin-based catalyst showed remarkable H₂ and CO evolution at ambient conditions. Using monochromatic light (420 nm), the highest values of apparent quantum yields reached 22.8 and 12.5% for H₂ and CO, respectively. Photoluminescence spectra and photocurrent responses proved the efficient electron transfer between the hybrid photosensitizer and the molecular catalyst, which enhanced the performance of the present photocatalytic system. Mechanistic insights regarding the molecular catalyst were obtained using cyclic voltammetry, inferring the generation of Fe(I) species as a critical step in the photocatalytic decomposition of formic acid.