Reactively sputtered nickel oxide (NiOx) films provide transparent, antireflective, electrically conductive, chemically stable coatings that also are highly active electrocatalysts for the oxidation of water to O2(g). These NiOx coatings provide protective layers on a variety of technologically important semiconducting photoanodes, including textured crystalline Si passivated by amorphous silicon, crystalline n-type cadmium telluride, and hydrogenated amorphous silicon. Under anodic operation in 1.0 M aqueous potassium hydroxide (pH 14) in the presence of simulated sunlight, the NiOx films stabilized all of these self-passivating, high-efficiency semiconducting photoelectrodes for >100 h of sustained, quantitative solar-driven oxidation of water to O2(g).

Functionalization of semiconductor surfaces with organic moieties can change the charge distribution, surface dipole, and electric field at the interface. The modified electric field will shift the semiconductor band-edge positions relative to those of a contacting phase. Achieving 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 shifted relative to Si(111)-CH 3 samples by +0.27 V for n-Si and by up to +0.10 V for p-Si.Residual surface recombination limited the E oc of p-Si samples at high θ TFPA despite the favorable shift in the band-edge positions induced by the surface modification process.

A. Supporting Experimental Details. Surfaces. Wafers were cut with a diamondtipped scribe to the desired size and then rinsed sequentially with water, methanol (≥99.8%, EMD), acetone (≥99.5%, EMD), methanol, and water. Organic contaminants were removed and the surfaces were oxidized by immersing the wafers in a freshly prepared piranha solution (1:3 v/v of 30% H 2 O 2 (aq) (EMD): 18 M H 2 SO 4 (EMD)) at 90-95 °C for 10-15 min. The wafers were rinsed with copious amounts of water and immersed in buffered HF(aq) (semiconductor grade, Transene Co., Inc.) for 18 s followed by another water rinse. Atomically flat H-Si (111) surfaces were prepared by immersing the wafers in an Ar(g)-purged solution of NH 4 F(aq). Preparation of Atomically 1-2Wafers with a miscut angle of 0.5° were etched for 5.5 min, while wafers with a miscut angle of 0.1° were etched for 9.0 min to obtain optimal terrace size. The solution was purged throughout the etching process and the wafers were agitated after each minute of etching to remove bubbles S2 that formed on the surface. After etching, the wafers were rinsed with water and dried under a stream of Ar(g). Surfaces. Cl-Si(111) surfaces were prepared inside a N 2 (g)-purged glovebox with <10 ppm O 2 . A saturated solution of PCl 5 (≥99.998% metal basis, Alfa Aesar) in chlorobenzene (anhydrous, ≥99.8%, Sigma-Aldrich) was preheated with an initiating amount (<1 mg mL -1 ) of benzoyl peroxide (≥98%, Sigma-Aldrich) for 1-2 min. The H-Si (111) wafers were rinsed with chlorobenzene and then reacted in the PCl 5 solution at 90 ± 2 °C for 45 min. 1,3 Upon completion of the reaction, the solution was drained and the wafers were rinsed with copious amounts of chlorobenzene, followed by tetrahydrofuran (THF, anhydrous, inhibitor-free, ≥99.9%, Sigma-Aldrich). Surfaces. Br-Si(111) surfaces were prepared by reaction under ambient light at 22 °C of H-Si(111) with Br 2 (g) in a drying chamber connected to a vacuum line as well as to a reservoir of Br 2 (l). Immediately after anisotropic etching, H-Si (111) samples were placed inside the drying chamber, which was then evacuated to <20 mTorr. The sample was sealed under vacuum and the Br 2 (l) reservoir was quickly opened and closed to allow a visible amount of Br 2 (g) into the evacuated drying chamber. The reaction was allowed to proceed for 10 s, after which the Br 2 (g) was removed by vacuum to a pressure of <20 mTorr. Preparation of Preparation of of 2, 4The sample was sealed under vacuum and transferred to a N 2 (g)-purged glovebox.B. Supporting Instrumentation Details. Transmission Infrared Spectroscopy.A custom attachment allowed Si samples (1.3 × 3.2 cm) to be mounted such that the incident IR beam was either 74° or 30° with respect to the sample surface normal. At 74° (Brewster's angle for Si), IR modes parallel and perpendicular to the surface are observed, and at 30°, parallel modes remain visible, while perpendicular modes S3 are greatly diminished in intensity. 5 Reported spectra are averages of 1500 consecutive scans collected at a resolu...

Hydrated electron lifetimes in photodetached sulfite solutions at intermediate pH (5–10) are limited by HSO3– rather than proton (H+) quenching.

H-Si(111) surfaces have been reacted with liquid methanol (CH 3 OH) in the absence or presence of a series of oxidants and/or illumination. Oxidant-activated methoxylation of HSi(111) surfaces was observed in the dark after exposure to CH 3 OH solutions that contained the one-electron oxidants acetylferrocenium, ferrocenium, or 1,1'-dimethylferrocenium. The oxidant-activated reactivity toward CH 3 OH of intrinsic and n-type H-Si(111) surfaces increased upon exposure to ambient light. The results suggest that oxidant-activated methoxylation requires that two conditions be met: (1) the position of the quasi-Fermi levels must energetically favor oxidation of the H-Si(111) surface and (2) the position of the quasi-Fermi levels must energetically favor reduction of an oxidant in solution. Consistently, illuminated n-type HSi(111) surfaces underwent methoxylation under applied external bias more rapidly and at more negative potentials than p-type H-Si(111) surfaces. The results under potentiostatic control indicate that only conditions that favor oxidation of the H-Si(111) surface need be met, with charge balance at the surface maintained by current flow at the back of the electrode. The results are described by a mechanistic framework that analyzes the positions of the quasi-Fermi levels relative to the energy levels relevant for each system.

Thin films of nickel oxide (NiOx), cobalt oxide (CoOx) and nickel–cobalt oxide (NiCoOx) produced integrated, protected Si (111) photoanodes integrated, protected Si photoanodes that did not require deposition of a separate heterogeneous electrocatalyst for water oxidation.

The cover picture shows that nitrate and especially nitrite rapidly oxidize cob(I)alamin to cob(II)alamin. Enzyme‐bound cob(I)alamin is a short‐lived species whose formation is essential for the activity of both mammalian vitamin B12 dependent enzymes. Nitrite and nitrate, intracellular levels of which are elevated during oxidative/nitrosative stress as a consequence of elevated nitric oxide levels, are generally considered to be benign species. Details are discussed in the article by N. E. Brasch et al. on p. 913 ff. The cover picture was designed by Rohan S. Dassanayake. magnified image

The behavior of n-Si(111) photoanodes covered by monolayer sheets of fluorinated graphene (F-Gr) was investigated under a range of chemical and electrochemical conditions. The electrochemical behavior of n-Si/F-Gr and np(+)-Si/F-Gr photoanodes was compared to hydride-terminated n-Si (n-Si-H) and np(+)-Si-H electrodes in contact with aqueous Fe(CN)6(3-/4-) and Br2/HBr electrolytes as well as in contact with a series of outer-sphere, one-electron redox couples in nonaqueous electrolytes. Illuminated n-Si/F-Gr and np(+)-Si/F-Gr electrodes in contact with an aqueous K3(Fe(CN)6/K4(Fe(CN)6 solutions exhibited stable short-circuit photocurrent densities of ∼10 mA cm(-2) for 100,000 s (>24 h), in comparison to bare Si electrodes, which yielded nearly a complete photocurrent decay over ∼100 s. X-ray photoelectron spectra collected before and after exposure to aqueous anodic conditions showed that oxide formation at the Si surface was significantly inhibited for Si electrodes coated with F-Gr relative to bare Si electrodes exposed to the same conditions. The variation of the open-circuit potential for n-Si/F-Gr in contact with a series of nonaqueous electrolytes of varying reduction potential indicated that the n-Si/F-Gr did not form a buried junction with respect to the solution contact. Further, illuminated n-Si/F-Gr electrodes in contact with Br2/HBr(aq) were significantly more electrochemically stable than n-Si-H electrodes, and n-Si/F-Gr electrodes coupled to a Pt catalyst exhibited ideal regenerative cell efficiencies of up to 5% for the oxidation of Br(-) to Br2.