Solar CO2 hydrogenation by photocatalytic foams

Abstract

Here we report the enhanced light penetration and mass transfer efficiency of photocatalytic foams to convert CO2 to CO. The viability of utilizing a metallic foam as a model photocatalyst support is used to evaluate the photochemical and thermochemical reverse water gas shift reaction catalyzed by photoactive indium oxide hydroxide nanorods uniformly coated on nickel foams. A light-enhanced CO production rate up to 130% higher than the dark CO production was achieved through enhanced light penetration. A remarkably high thermochemical CO production rate of 0.75 mmol gcat−1 h−1 was achieved at 295 °C. Whilst several approaches to optimization of photocatalyst morphology at the nanoscale have been successful in extending electron hole-pair lifetime and modifying the site of reactions, these advantages cannot be significantly realized unless microscale to macroscale structuring efforts, that shorten the path length for diffusion of the reactant gas molecule and lengthen photon penetration to these catalytic sites are integrated. The superior catalytic performance of the indium oxide hydroxide nanorods on an optimized coated foam configuration compared to the performance of packed bed and thin film configurations demonstrates the critical importance of using structured supports in scale up of future photocatalytic processes.