Solar Water Splitting with a Hydrogenase Integrated in Photoelectrochemical Tandem Cells.

Dong Heon Nam,Stephan Hofmann,Kenichi Nakanishi,Nikolay Kornienko,Barnaby Slater,Ingo Zebger,Nina Heidary,Juan C Fontecilla‐Camps,Jenny Z Zhang,Chan Beum Park,Erwin Reisner,Katarzyna P Sokol,Virgil Andrei,Andreas Wagner

doi:10.1002/anie.201805027

Abstract

Hydrogenases (H2ases) are benchmark electrocatalysts for H2 production, both in biology and (photo)catalysis in vitro. We report the tailoring of a p‐type Si photocathode for optimal loading and wiring of H2ase through the introduction of a hierarchical inverse opal (IO) TiO2 interlayer. This proton‐reducing Si|IO‐TiO2|H2ase photocathode is capable of driving overall water splitting in combination with a photoanode. We demonstrate unassisted (bias‐free) water splitting by wiring Si|IO‐TiO2|H2ase to a modified BiVO4 photoanode in a photoelectrochemical (PEC) cell during several hours of irradiation. Connecting the Si|IO‐TiO2|H2ase to a photosystem II (PSII) photoanode provides proof of concept for an engineered Z‐scheme that replaces the non‐complementary, natural light absorber photosystem I with a complementary abiotic silicon photocathode.

Highlights

We report the tailoring of a p-type Si photocathode for optimal loading and wiring of H2ase through the introduction of a hierarchical inverse opal (IO) TiO2 interlayer
The H2 evolving Clostridium acetobutylicum [FeFe] hydrogenase HydA, adsorbed on a pyrolytic graphite edge electrode, had been connected to a porphyrin-sensitized TiO2 photoanode. This PEC cell relied on the consumption of sacrificial NADH,[1d] whereas we demonstrate overall water splitting in this work
BiVO4 was selected owing to its stability under the neutral pH conditions required for the H2ase, and its high photovoltage and currents are in principle suitable for bias-free water splitting when paired with a silicon photocathode.[9,10a,b] The synthesized BiVO4 is crystalline and exhibits a film thickness of approximately 650 nm with a nanoporous surface structure

Summary

Introduction

This proton-reducing Si j IO-TiO2 j H2ase photocathode is capable of driving overall water splitting in combination with a photoanode. BiVO4 is a well-established photoanode for water oxidation,[9] which was synthesized on FTO-coated glass according to previous reports.[10] BiVO4 was selected owing to its stability under the neutral pH conditions required for the H2ase, and its high photovoltage and currents are in principle suitable for bias-free water splitting when paired with a silicon photocathode.[9,10a,b] The synthesized BiVO4 is crystalline and exhibits a film thickness of approximately 650 nm with a nanoporous surface structure (see Figure S12 for SEM images, XRD pattern, and UV/Vis spectrum).

Results

Conclusion