Leave No Photon Behind: Artificial Intelligence in Multiscale Physics of Photocatalyst and Photoreactor Design.

Although solar fuels photocatalysis offers the promise of converting carbon dioxide directly with sunlight as commercially scalable solutions have remained elusive over the past few decades, despite significant advancements in photocatalysis band-gap engineering and atomic site activity. The primary challenge lies not in the discovery of new catalyst materials, which are abundant, but in overcoming the bottlenecks related to material-photoreactor synergy. These factors include achieving photogeneration and charge-carrier recombination at reactive sites, utilizing high mass transfer efficiency supports, maximizing solar collection, and achieving uniform light distribution within a reactor.

Facilely Achieved Self-Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100.

Photodiodes are fundamental components in modern optoelectronics. Heterojunction photodiodes, simply configured by two different contact materials, have been a hot research topic for many years. Currently reported self-biased heterojunction photodiodes routinely have external quantum efficiency (EQE) significantly below 100% due to optical and electrical losses.

A one-step, tunable method of selective reactive sputter deposition as a wrinkling approach for silver/polydimethylsiloxane for electrically conductive pliable surfaces.

The wrinkle period and morphology of a metal thin film on an elastic substrate is typically controlled by modifying the substrate before carrying out additional metal deposition steps. Herein, we show that a simultaneously selective and reactive sputtering plasma that modifies the surface of a polydimethylsiloxane (PDMS) substrate while not reacting with the metal during the deposition process decreases the wrinkle wavelength and induces additional wrinkling components and features such as ripples or folds. The selective reaction of the nitrogen plasma with PDMS functionalizes the siloxane surface into silicon oxynitride.

Near-Perfect Absorbing Copper Metamaterial for Solar Fuel Generation.

Metamaterials are a new class of artificial materials that can achieve electromagnetic properties that do not occur naturally, and as such they can also be a new class of photocatalytic structures. We show that metal-based catalysts can achieve electromagnetic field amplification and broadband absorption by decoupling optical properties from the material composition as exemplified with a ZnO/Cu metamaterial surface comprising periodically arranged nanocubes. Through refractive index engineering close to the index of air, the metamaterial exhibits near-perfect 98% absorption.

Construction of New Active Sites: Cu Substitution Enabled Surface Frustrated Lewis Pairs over Calcium Hydroxyapatite for CO Hydrogenation.

Calcium hydroxyphosphate, Ca (PO ) (OH) , is commonly known as hydroxyapatite (HAP). The acidic calcium and basic phosphate/hydroxide sites in HAP can be modified via isomorphous substitution of calcium and/or hydroxide ions to enable a cornucopia of catalyzed reactions. Herein, isomorphic substitution of Ca ions by Cu ions especially at very low levels of exchange created new analogs of molecular surface frustrated Lewis pairs (SFLPs) in Cu Ca (PO ) (OH) , thereby boosting its performance metrics in heterogeneous CO photocatalytic hydrogenation.

Waveguide photoreactor enhances solar fuels photon utilization towards maximal optoelectronic - photocatalytic synergy.

A conventional light management approach on a photo-catalyst is to concentrate photo-intensity to enhance the catalytic rate. We present a counter-intuitive approach where light intensity is distributed below the electronic photo-saturation limit under the principle of light maximization. By operating below the saturation point of the photo-intensity induced hydroxide growth under reactant gaseous H+CO atmosphere, a coating of defect engineered InO(OH) nanorod Reverse Water Gas Shift solar-fuel catalyst on an optical waveguide outperforms a coated plane by a factor of 2.

Plasmonic Titanium Nitride Facilitates Indium Oxide CO Photocatalysis.

Nanoscale titanium nitride TiN is a metallic material that can effectively harvest sunlight over a broad spectral range and produce high local temperatures via the photothermal effect. Nanoscale indium oxide-hydroxide, In O (OH) , is a semiconducting material capable of photocatalyzing the hydrogenation of gaseous CO ; however, its wide electronic bandgap limits its absorption of photons to the ultraviolet region of the solar spectrum. Herein, the benefits of both nanomaterials in a ternary heterostructure: TiN@TiO @In O (OH) are combined.

Relating surface defect energetics with reactant gas adsorption during the photo-catalytic reduction of CO by partially hydrolyzed InO nanorods.

Photo-Induced Transient Current Spectroscopy (PICTS) is a versatile technique for measurements of defect state energies and densities in photo-active materials. It is suitable for investigating the surface-gas adsorbate behavior and the defect characteristics of defect laden In2O3-x(OH)y nanorods, having oxygen vacancies and hydroxide surface groups, under in situ reactor conditions of dark ambient temperature, dark 150 °C and photo-illuminated 150 °C, for the photo-assisted Reverse Water Gas Shift reaction. From glovebox-protected X-ray Photoelectron Spectroscopy and in situ PICTS measurements we determined that the reduction of CO2 is associated with heterolytic dissociation of H2 into In-H§- and HO-H§+ centres accompanied by an increase in average carrier trap energies; increased carbonate formation in a photo/thermal reactor state of H2 + CO2, and an average trap energy decrease of 0.

Shining light on CO: from materials discovery to photocatalyst, photoreactor and process engineering.

Heterogeneous catalysis, a process in which the reaction of gaseous or liquid chemical reagents is facilitated at the surface of a solid material, is responsible for the majority of industrial-scale chemical and fuel production reactions. The energy required to drive these reactions has historically been derived from the combustion of non-renewable fossil fuels and carries an unavoidably large carbon footprint. More recently, the development of environmentally responsible and sustainable chemical industries is increasingly motivated by greenhouse gas-induced climate change, thus creating demand for eco-friendly heterogeneous catalytic processes.

Hybrid Photo- and Thermal Catalyst System for Continuous CO Reduction.

Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy.

Black indium oxide a photothermal CO hydrogenation catalyst.

Nanostructured forms of stoichiometric InO are proving to be efficacious catalysts for the gas-phase hydrogenation of CO. 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 InO 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.

Plasmonics of Diffused Silver Nanoparticles in Silver/Nitride Optical Thin Films.

Metal-dielectric multilayers are versatile optical devices that can be designed to combine the visible transmittance of dielectrics with the electronic properties of metals for plasmonic and meta-material applications. However, their performances are limited by an interfacial optical absorption often attributed entirely to the metal surface roughness. Here, we show that during deposition of AlN/Ag/AlN and SiN/Ag/SiN multilayers, significant diffusion of Ag into the top dielectric layer form Ag nanoparticles which excite localized surface plasmon resonances that are primarily responsible for the interfacial optical absorption.

Synergistic Coupling of Photo and Thermal Conditions for Enhancing CO Reduction Rates in the Reverse Water Gas Shift Reaction.

The photocatalytic activity of nanostructured InO(OH) for the reverse water gas shift (RWGS) reaction CO + H → CO + HO can be greatly enhanced by substitution of Bi(III) for In(III) in the lattice of BiInO(OH). This behavior was hypothesized as the effect of the population and location of Bi(III) on the Lewis acidity and Lewis basicity of proximal hydroxide and coordinately unsaturated metal surface sites in BiInO(OH) acting synergistically as a frustrated Lewis acid-base pair reaction. Nonetheless, such photocatalytic activity is usually optimized in a specific batch reactor setup sequence, with H as an initial gas input under photo and thermal conditions before introducing CO.

X-ray Photospectroscopy and Electronic Studies of Reactor Parameters on Photocatalytic Hydrogenation of Carbon Dioxide by Defect-Laden Indium Oxide Hydroxide Nanorods.

In the study reported herein, glovebox-protected X-ray photoelectron spectroscopy (XPS) and in situ Hall charge carrier measurements provide new insights into the surface physical chemistry of gaseous H, CO, and H+CO combined with nanostructured InO(OH) nanorods, which ensue under photochemical and thermochemical operating conditions. Heterolytic dissociation of H in H-only atmosphere appears to occur mainly under dark and ambient temperature conditions, while the greatest amount of OH shoulder expansion in H+CO atmosphere appears to mainly occur under photoilluminated conditions. These results correlate with those of the Hall measurements, which show that the prevalence of homolytic over heterolytic dissociation at increasing temperatures leads to a steeper rate of increase in carrier concentrations; and that H adsorption is more prevalent than CO in H+CO photoillumination conditions.

In Situ Electronic Probing of Photoconductive Trap States for the Catalytic Reduction of CO by InOOH Nanorods.

We use photoconductivity time, optical absorption, and electron quantum efficiency measurements under in situ reactant CO + H atmospheres to determine the role of surface trap states during photoreduction of CO to CO using InOOH nanorods of varied annealing times. Photocurrent decay trends show an asymmetric energy distribution of surface barrier potentials with increased asymmetry from vacuum to CO + H. Urbach analysis shows crystalline disorder parameters of 0.

Tailoring Surface Frustrated Lewis Pairs of InO (OH) for Gas-Phase Heterogeneous Photocatalytic Reduction of CO by Isomorphous Substitution of In with Bi.

Frustrated Lewis pairs (FLPs) created by sterically hindered Lewis acids and Lewis bases have shown their capacity for capturing and reacting with a variety of small molecules, including H and CO, and thereby creating a new strategy for CO reduction. Here, the photocatalytic CO reduction behavior of defect-laden indium oxide (InO (OH) ) is greatly enhanced through isomorphous substitution of In with Bi, providing fundamental insights into the catalytically active surface FLPs (i.e.

Spatial Separation of Charge Carriers in In2O3-x(OH)y Nanocrystal Superstructures for Enhanced Gas-Phase Photocatalytic Activity.

The development of strategies for increasing the lifetime of photoexcited charge carriers in nanostructured metal oxide semiconductors is important for enhancing their photocatalytic activity. Intensive efforts have been made in tailoring the properties of the nanostructured photocatalysts through different ways, mainly including band-structure engineering, doping, catalyst-support interaction, and loading cocatalysts. In liquid-phase photocatalytic dye degradation and water splitting, it was recently found that nanocrystal superstructure based semiconductors exhibited improved spatial separation of photoexcited charge carriers and enhanced photocatalytic performance.

Photoexcited Surface Frustrated Lewis Pairs for Heterogeneous Photocatalytic CO2 Reduction.

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.

Low-temperature degradation in zirconia with a porous surface.

Today there is growing interest in zirconia in the dental field, but its use is still recent. Dental zirconia is mainly found in the form of yttria-stabilized zirconia crowns, bridges and abutments, and several companies are developing zirconia implants as an alternative to the standard biomedical grade titanium. In order to favor bone in-growth and osseointegration of zirconia implants, several strategies are now being explored to process rough and/or porous surfaces.