Defect Engineering of Bismuth Oxyiodide by IO₃^– Doping for Increasing Charge Transport in Photocatalysis

Defect engineering is regarded as one of the most active projects to monitor the chemical and physical properties of materials, which is expected to increase the photocatalytic activities of the materials. Herein, oxygen vacancies and IO₃^– doping are introduced into BiOI nanosheets via adding NaH₂PO₂, which can impact the charge carrier dynamics of BiOI photocatalysts, such as its excitation, separation, trap, and transfer. These oxygen-deficient BiOI nanosheets display attractive photocatalytic activities of gaseous formaldehyde degradation and methyl orange under visible light irradiation, which are 5 and 3.5 times higher than the BiOI samples, respectively. Moreover, the comodified BiOI also displayed superior cycling stability and can be used for practical application. This work not only develops an effective strategy for fabricating oxygen vacancies but also offers deep insight into the impact of surface defects in enhancing photocatalysis

Carbon Dots Sensitized BiOI with Dominant {001} Facets for Superior Photocatalytic Performance

Degrading and removing harmful compounds by the use of semiconductor photocatalysts has been testified to be and effective and attractive green technique in wastewater treatment. Herein, carbon dots sensitized BiOI with highly exposed {001} facets has been prepared and used to study the photocatalytic degradation of methyl orange (MO). Due to the improved charge separation, transfer, and optical absorption, the photocatalytic performance for methyl orange degradation of the carbon dots/{001} BiOI nanosheets is 4 times higher than that of the {001} BiOI nanosheets under visible light irradiation. Additionally, the carbon dots/{001} BiOI nanosheets also have superior stability after 5 cyclings

Ytterbium-Catalyzed Hydroboration of Aldehydes and Ketones

The well-defined heavy rare-earth ytterbium iodide complex <b>1</b> (L₂YbI) has been successfully employed as an efficient catalyst for the hydroboration of a wide range of aldehydes and ketones with pinacolborane (HBpin) at room temperature. The protocol requires low catalyst loadings (0.1–0.5 mol %) and proceeds rapidly (>99% conversion in <10 min). Additionally, catalyst <b>1</b> shows a good functional group tolerance even toward the hydroxyl and amino moieties and displays chemoselective hydroboration of aldehydes over ketones under mild conditions

Direct <i>In Situ</i> Measurement of Quantum Efficiencies of Charge Separation and Proton Reduction at TiO₂‑Protected GaP Photocathodes

Photoelectrochemical solar fuel generation at the semiconductor/liquid interface consists of multiple elementary steps, including charge separation, recombination, and catalytic reactions. While the overall incident light-to-current conversion efficiency (IPCE) can be readily measured, identifying the microscopic efficiency loss processes remains difficult. Here, we report simultaneous in situ transient photocurrent and transient reflectance spectroscopy (TRS) measurements of titanium dioxide-protected gallium phosphide photocathodes for water reduction in photoelectrochemical cells. Transient reflectance spectroscopy enables the direct probe of the separated charge carriers responsible for water reduction to follow their kinetics. Comparison with transient photocurrent measurement allows the direct probe of the initial charge separation quantum efficiency (ϕCS) and provides support for a transient photocurrent model that divides IPCE into the product of quantum efficiencies of light absorption (ϕabs), charge separation (ϕCS), and photoreduction (ϕred), i.e., IPCE = ϕabsϕCSϕred. Our study shows that there are two general key loss pathways: recombination within the bulk GaP that reduces ϕCS and interfacial recombination at the junction that decreases ϕred. Although both loss pathways can be reduced at a more negative applied bias, for GaP/TiO2, the initial charge separation loss is the key efficiency limiting factor. Our combined transient reflectance and photocurrent study provides a time-resolved view of microscopic steps involved in the overall light-to-current conversion process and provides detailed insights into the main loss pathways of the photoelectrochemical system

Discovery of a Hybrid System for Photocatalytic CO₂ Reduction via Attachment of a Molecular Cobalt-Quaterpyridine Complex to a Crystalline Carbon Nitride

While recent reports have demonstrated the attachment of molecular catalysts to amorphous, graphitic carbon nitrides (g-CN) for light-driven CO2 reduction, approaches to the utilization of crystalline carbon nitrides have remained undiscovered. Herein, a functional hybrid photocatalyst system has been found using a crystalline carbon nitride semiconductor, poly(triazine imide) lithium chloride (PTI-LiCl), with a surface-attached CoCl2(qpy-Ph-COOH) catalyst for CO2 reduction. The molecular catalyst attaches to PTI-LiCl at concentrations from 0.10 to 4.30 wt % and exhibits ∼96% selectivity for CO production in a CO2-saturated, aqueous 0.5 M KHCO3 solution. Optimal loadings were found to be within 0.42–1.04 wt % with rates between 1,400 and 1,550 μmol CO/g·h at an irradiance of 172 mW/cm2 (λ = 390 nm) and apparent quantum yields of ∼2%. This optimized loading is postulated to represent a balance between maximal turnover frequency (TOF; 300+ h–1) and excess catalyst that can limit excited-electron lifetimes, as probed via transient absorption spectroscopy. An increase in the incident irradiance yields a concomitant increase in the TOFs and CO rates only for the higher catalyst loadings, reaching up to 2,149 μmol CO/g·h with a more efficient use of the catalyst surface capacity. The lower catalyst loadings, by comparison, already function at maximal TOFs. Higher surface loadings are also found to help mitigate deactivation of the molecular catalysts during extended catalytic testing (>24 h) owing to the greater net surface capacity for CO2 reduction, thus representing an effective strategy to extend lifetime. The hybrid particles can be deposited onto an FTO substrate to yield ∼60% Faradaic efficiency for photoelectrochemical CO production at −1.2 V vs Ag/AgCl bias. In summary, these results demonstrate the synergistic combination of a crystalline carbon nitride with a molecular catalyst that achieves among the highest known rates in carbon-nitride systems for the light-driven CO2 reduction to CO in aqueous solution with >95% selectivity