Plasmonic nanostructured Zn/ZnO composite enhances carbonic anhydrase driven photocatalytic hydrogen generation

Abstract

Hydrogen is produced from water by electrolysis or photolysis. Although, photocatalysis demands significantly less energy, it has several problem issues; slower production rate, consumption of sacrificial donors or need for expensive noble metals. Here, we report substantial increase in the rate of hydrogen evolution without the use of sacrificial donors or noble metals. We demonstrate appreciable hydrogen generation by coupling biomimetic carbonation with common metal driven plasmonic photocatalysis. Our process has three parts. First, zinc leads to the formation of Zn/ZnO composite, which acts as the proximate photocatalyst. Second, specific illumination operates on the composite via Surface Plasmon Resonance (SPR), a phenomenon in which photons activated nanoparticles exhibit local heating, concentration and redistribution of the incident light and release of electrons. Third, carbonic anhydrase catalyzes the hydrolysis of water by CO2 to provide both protons and bicarbonate ions critical to the process. In sum, protons derived from water combine with electrons derived photocatalytically from Zn/ZnO to yield hydrogen. Only photons and water are consumed and only hydrogen is produced. The SPR sensitive Zn/ZnO composite generates hydrogen evolution at a rate of 1238μmolh−1, an unprecedented enhancement (16.7-fold) over zinc micro particles − Zn(M) alone. The system is unique and low cost and avoids the use of noble metal and organic donors.