Photobiocatalytic H2 evolution of GaN:ZnO and [FeFe]-hydrogenase recombinant Escherichia coli

The need for sustainable, renewable and low-cost approaches is a driving force behind the development of solar-to-H₂ conversion technologies. This study aims to develop a new strategy using a visible-light photocatalyst coupled to a biocatalyst for H₂ production. Photocatalytic methyl viologen (MV²⁺) reduction activity was investigated to discover active oxynitrides. In comparative studies with LaTiO₂N, BaTaO₂N and Ta₃N₅, it was revealed that the suitable surface area, band gap and band edge potentials are some physical factors that are responsible for the photocatalytic behaviors of GaN:ZnO in MV²⁺ reduction. The activity is enhanced at higher concentrations and the alkaline pH of triethanolamine (TEOA). The expression of an active [FeFe]-hydrogenase from Escherichia coli (Hyd⁺E. coli) as a recombinant biocatalyst was confirmed by its MV˙⁺-dependent H₂ production activity. In the photobiocatalytic system of GaN:ZnO and Hyd⁺E. coli, the rate of H₂ production reached the maximum level in the presence of MV²⁺ as an electron mediator at neutral pH as a biocompatible condition. The present work reveals a novel hybrid system for H₂ production using visible-light active GaN:ZnO coupled to Hyd⁺E. coli, which shows the feasibility of being developed for photobiocatalytic H₂ evolution under solar light.