Band gap narrowing is important and advantageous for potential visible light photocatalytic applications involving metal oxide nanostructures. This paper reports a simple biogenic approach for the promotion of oxygen vacancies in pure zinc oxide (p-ZnO) nanostructures using an electrochemically active biofilm (EAB), which is different from traditional techniques for narrowing the band gap of nanomaterials. The novel protocol improved the visible photocatalytic activity of modified ZnO (m-ZnO) nanostructures through the promotion of oxygen vacancies, which resulted in band gap narrowing of the ZnO nanostructure (Eg = 3.05 eV) without dopants. X-ray diffraction, UV-visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy, Raman spectroscopy, photoluminescence spectroscopy and high resolution transmission electron microscopy confirmed the oxygen vacancy and band gap narrowing of m-ZnO. m-ZnO enhanced the visible light catalytic activity for the degradation of different classes of dyes and 4-nitrophenol compared to p-ZnO, which confirmed the band gap narrowing because of oxygen defects. This study shed light on the modification of metal oxide nanostructures by EAB with a controlled band structure.

We report a simple biogenic-route to narrow the band gap of TiO2 nanocrystals for visible light application by offering a greener method. When an electrochemically active biofilm (EAB) was challenged with a solution of Degussa-TiO2 using sodium acetate as the electron donor, greyish blue-colored TiO2 nanocrystals were obtained. A band gap study showed that the band gap of the modified TiO2 nanocrystals was significantly reduced (E(g) = 2.85 eV) compared to the unmodified white Degussa TiO2 (E(g) = 3.10 eV).

This review provides an overview of the cross-disciplinary field of semi-artificial photosynthesis, which combines strengths of biocatalysis and artificial photosynthesis to develop new concepts and approaches for solar-to-chemical conversion.

Harvesting solar energy to convert CO 2 into chemical fuels is a promising technology to curtail the growing atmospheric CO 2 levels and alleviate the global dependence on fossil fuels. However, the assembly of efficient and robust systems for the selective photoconversion of CO 2 without sacrificial reagents and external bias remains a challenge. Here, we present a photocatalyst sheet that converts CO 2 and H 2 O into formate and O 2 as a potentially scalable technology for CO 2 utilisation. This technology integrates La and Rh-doped SrTiO 3 (SrTiO 3 :La,Rh) and Mo-doped BiVO 4 (BiVO 4 :Mo) light absorbers modified by phosphonated Co(II) bis(terpyridine) and RuO 2 catalysts onto a gold layer. The monolithic device provides a solar-to-formate conversion efficiency of 0.08±0.01% with a selectivity for formate of 97±3%. As the device operates wirelessly and uses water as an electron donor, it offers a versatile strategy toward scalable and sustainable CO 2 reduction using molecular-based hybrid photocatalysts.

An electrochemically active biofilm was utilized for modification of CeO2 nanostructures.