Abstract
Photoelectrooxidation of chloride ions to chlorine with co-production of hydrogen by water reduction has been proposed as a means of decreasing the net solar hydrogen production cost. So far, however, most such solar-to-chlorine production systems use cost-prohibitive materials and/or show rather small faradaic yield or stability. Here we report the development of earth-abundant, nanostructured bismuth vanadate/tungsten oxide (BiVO4/WO3) photoanode assemblies that operate in acidic sodium chloride solution (pH 1; 4 M) to produce chlorine while generating hydrogen at the dark cathode. We show that electrodeposition of 20 nm WO3 coating protects BiVO4 from harsh pH and oxidative environments while being catalytically active for chlorine evolution. The heterostructured BiVO4/WO3 photoanodes yield average photocurrent densities of 2.5 ± 0.3 mA cm−2 at 1.42 VRHE (Reversible Hydrogen Electrode) under 1 sun illumination. After two hours of continuous illumination, the best performing devices demonstrate faradaic efficiencies of 85% for chlorine production and ~100% for hydrogen production.
Highlights
Photoelectrooxidation of chloride ions to chlorine with co-production of hydrogen by water reduction has been proposed as a means of decreasing the net solar hydrogen production cost
The BiVO4/WO3 nanostructured films were deposited on conductive fluorine-doped tin oxide (FTO) coated glass substrate using a two-step process
The first step is the fabrication of crystalline BiVO4 light absorber unit following previously reported methods[17], where electrodeposited bismuth oxyiodide (BiOI) is used as a precursor to form BiVO4. (Fig. 1a, c) shows a top view and cross-sectional scanning electron microscopy (SEM) images of the bare BiVO4 electrode
Summary
Photoelectrooxidation of chloride ions to chlorine with co-production of hydrogen by water reduction has been proposed as a means of decreasing the net solar hydrogen production cost. Most such solar-to-chlorine production systems use cost-prohibitive materials and/or show rather small faradaic yield or stability. In the past few decades, revolutionary advances have been made in developing PEC water splitting systems that can produce H2 with solar-to-H2 (STH) efficiencies exceeding 10%2,3. While efforts to lower the H2 production cost using low-cost materials have been extensively pursued, a key technical and economic challenge to solar water splitting processes is the 4 electron oxidation of water which is slow kinetically and results in the production of limited economic value O2 (Eq 1)[4,5,6,7]. Accompanied by water reduction at the cathode to produce H2, could provide an attractive, cost-effective alternative to water oxidation[8,9,10]
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