Nanostructuring of semiconductor films offers the potential means for producing photoelectrodes with improved minority charge carrier collection. Crucial to the effective operation of the photoelectrode is also the choice of a suitable electrolyte. The behaviour of the nanostructured WO₃ photoanodes in methane sulfonic acid solutions, which allow one to obtain large, perfectly stable visible-light driven water splitting photocurrents, is discussed. The important effect of the electrolyte concentration upon the current distribution and the related photocurrent losses within the nanoporous photoelectrodes is pointed out.

Coupling the photo-oxidation of biomass derived substrates with water splitting in a photoelectrochemical (PEC) cell is a broadly discussed approach intended to enhance efficiency of hydrogen generation at the cathode. Here, we report a PEC device employing a nanostructured semitransparent WO₃ photoanode that, irradiated with simulated solar light achieves large photocurrents of 6.5 mA cm⁻² through oxidation of glucose, a common carbohydrate available in nature that can be obtained by processing waste biomass. The attained photocurrents are in a large part due to the occurrence of the photocurrent doubling, where oxidation of glucose by the photogenerated positive hole is followed by injection by the formed intermediate of an electron into the conduction band of WO_3. Selection of an appropriate supporting electrolyte enabled effective reforming of glucose into valuable products: gluconic and glucaric acids, erythrose and arabinose with up to 64% total Faradaic yield attained at ca 15% glucose conversion.

The use of an aqueous electrolyte containing dissolved CO₂ enabled revealing of an unusually intense photoemission from a bulk silver electrode. The observed cathodic photocurrent exhibits a sharp peak at ∼360 nm corresponding to the energy of surface plasmons in silver. The amount and the spectral distribution of the photocurrent are strongly affected by the extent of roughness of the silver surface. In particular, an electrochemical roughening procedure, analogous to that leading to the surface enhancement of Raman scattering (SERS) at silver, causes appearance of a long tail on the low‐energy side of the photoemission spectra. In consequence, significant photocurrents, corresponding to a quantum yield of ∼7×10⁻³, are observed for the deliberately roughened silver electrodes illuminated with the wavelength of 514 nm, most frequently used in SERS experiments. It is postulated that this intense photoemission, discovered in the presence of CO₂ in the solution, equally takes place in the absence of scavengers. However, in the latter case no significant photocurrents can be detected as most of the photoemitted electrons (solvated or not) return back to the electrode.