In this study we investigated, theoretically and experimentally, the unique photoactive behavior of pristine and defected indium oxide surfaces providing fundamental insights into their excited state properties as well as an explanation for the experimentally observed enhanced activity of defected indium oxide surfaces for the gas-phase reverse water gas shift reaction, CO2 + H2 + hν→ CO + H2O in the light compared to the dark. To this end, a detailed excited-state study of pristine and defected forms of indium oxide (In2O3, In2O3-x, In2O3(OH)y and In2O3-x(OH)y) surfaces was performed using time dependent density functional theory (TDDFT) calculations, the results of which were supported experimentally by transient absorption spectroscopy and photoconductivity measurements. It was found that the surface frustrated Lewis pairs (FLPs) created by a Lewis acidic coordinately unsaturated surface indium site proximal to an oxygen vacancy and a Lewis basic surface hydroxide site in In2O3-x(OH)y become more acidic and basic and hence more active in the ES compared to the GS. This provides a theoretical mechanism responsible for the enhanced activity and reduced activation energy of the photochemical reverse water gas shift reaction observed experimentally for In2O3-x(OH)y compared to the thermochemical reaction. This fundamental insight into the role of photoexcited surface FLPs for catalytic CO2 reduction could lead to improved photocatalysts for solar fuel production.

Nanostructured forms of stoichiometric In 2 O 3 are proving to be efficacious catalysts for the gas-phase hydrogenation of CO 2. These conversions can be facilitated using either heat or light; however, until now, the limited optical absorption intensity evidenced by the pale-yellow color of In 2 O 3 has prevented the use of both together. To take advantage of the heat and light content of solar energy, it would be advantageous to make indium oxide black. Herein, we present a synthetic route to tune the color of In 2 O 3 to pitch black by controlling its degree of non-stoichiometry. Black indium oxide comprises amorphous non-stoichiometric domains of In 2 O 3-x on a core of crystalline stoichiometric In 2 O 3 , and has 100% selectivity towards the hydrogenation of CO 2 to CO with a turnover frequency of 2.44 s −1 .

Think thin! Colloidally stable ultrathin Bi2S3 nanowires (see picture), which display strong excitonic features never before seen in bismuth chalcogenides and extremely high extinction coefficients, have been synthesized on a gram‐scale. Nanostructures such as this are of very high technological potential for thermoelectric applications.

Rod-like In 2 O 3Àx (OH) y nanocrystal superstructure enhanced solar methanol synthesis with a remarkable production rate (0.06 mmol g cat À1 h À1 ) and selectivity (50%) at atmospheric pressure.

Modern society is experiencing an ever-increasing demand for energy to power a vast array of electrical and mechanical devices. As hydrocarbon resources dwindle, utilization of ample nuclear energy and abundant solar energy becomes more and more attractive. For 50 years, since the invention of the transistor, semiconductor devices that convert the energy of nuclear particles [1±5] or solar photons [6,7] to electric current have been investigated. However, conventional two-dimensional (2D) planar diode structures exhibit a number of inherent deficiencies that result in relatively low energy-conversion efficiencies. A unique three-dimensional (3D) porous silicon p±n diode has been developed to form the basis of a novel betavoltaic battery. Using tritium to demonstrate the proof-ofconcept, the 3D diode geometry demonstrated a tenfold enhancement of efficiency compared to that of the usual 2D betavoltaic device geometry. Given the similarity of the energyconversion physics for betavoltaic and photovoltaic devices, significant efficiency gains due to this 3D geometry might be expected for many types of photo detectors and solar cells. The 3D diode was constructed on porous silicon (PS), which consists of a network of pores formed by electrochemical anodization of silicon substrates. According to the pore size, PS is classified as microporous (£ 2 nm), mesoporous (2±50 nm), or macroporous (> 50 nm). Such porous morphologies define a very large internal surface area, [8,9] which retains most of the characteristics associated with planar surface geometries, particularly for macropores. [10,11] Numerous investigations have been done on the physical and chemical properties of this complex material. [8,9,12] Moreover, it has been demonstrated that PS components can be integrated into microelectronic circuits in order to construct practical devices. [13] To date, however, PS has only been used as an antireflection and surface-passivation layer [14,15] in photovoltaic devices. It is believed that this work reports the first construction of conformal p±n junctions in PS. PS diodes with a 3D p±n junction structure were created as illustrated schematically in Figure 1 (see Experimental for details). The continuous p±n junction can be visualized as a 2D ªsheetº that is deformed to produce a uniform p±n junction layer on every accessible surface of the pore space. The builtin voltage [16] of the diodes was estimated to be~0.8 V, assuming an n-dopant concentration of~5 10 18 cm ±3 and an abrupt p±n junction doping profile. The metallurgical junction was about 200 nm below the surface, and the estimated depletion width on the p-side of the junction was~1.4 lm. The efficacy of the pore anodization procedure was investigated by means of scanning electron microscopy (SEM