Amorphous TiO ₂ coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation

Abstract

Keeping semiconductors safe from harm Solar cells harvest the energy of sunlight to create electricity, but electricity is hard to store. Solar cells could also be used to make hydrogen from water, which can be stored as a fuel. Separating water into hydrogen and oxygen, however, presents challenges, especially if this is done directly by illuminating the anode that oxides water. Under the acidic or alkaline conditions needed for practical devices, semiconducting anode materials corrode during operation. Hu et al. now show that amorphous titanium dioxide coatings can protect semiconductors from alkaline corrosion while still allowing light through. Science , this issue p. 1005

CuO-Functionalized Silicon Photoanodes for Photoelectrochemical Water Splitting Devices

“…Several kinds of photoanodes have been used in this PEC set-up, including metal oxide semiconductors (Fe 2 O 3 , WO 3 , BiVO 4 , …), group III-V semiconductors (GaAs, GaP, InP, …) and amorphous silicon, all being excellent light absorbers and in most of the cases with good carrier mobility. [3][4][5] Among them, silicon is a particularly interesting candidate due to its low cost and good ability to absorb light. Unfortunately, silicon is only able to produce modest photocurrent densities of some µA/cm 2 , which decay very fast (in the minutes time scale) due to premature corrosion.…”

Solar-Powered Plasmon-Enhanced Heterogeneous Catalysis

“…A superficial treatment could improve the device's stability, but the implemented PEC would only reach few hundreds of hours of lifetime. Although the absorber protection realized through deposition of a passivation layer is an active research field [74,75], the ultimate approach would be the use of stable and earth-abundant materials.…”

Photoelectrochemical H2 Evolution with a Hydrogenase Immobilized on a TiO2‐Protected Silicon Electrode

“…The formation of TiO 2 was confirmed by X‐ray photoelectron spectroscopy (XPS) and by energy dispersive X‐ray spectroscopy (EDX) elemental analysis (Figures S1 b and S2). This method to generate an amorphous TiO 2 coating through solution processing at room temperature is simple and widely applicable,13 which is in contrast to conventionally employed atomic‐layer deposition or sputtering technologies to produce TiO 2 films 12a,12c. The FTO|TiO 2 surface was subsequently rinsed with water, the enzyme (3 μL of 8 μ m solution per cm 2 ) was drop‐cast onto the TiO 2 surface and the enzyme‐modified electrode rinsed with the electrolyte solution prior electrochemical measurements (50 m m MES (2‐(N‐morpholino)ethanesulfonic acid), at pH 6.0).…”