Light-Induced Dynamic Restructuring of Cu Active Sites on TiO2 for Low-Temperature H2 Production from Methanol and Water.

The structure and configuration of reaction centers, which dominantly govern the catalytic behaviors, often undergo dynamic transformations under reaction conditions, yet little is known about how to exploit these features to favor the catalytic functions. Here, we demonstrate a facile light activation strategy over a TiO2-supported Cu catalyst to regulate the dynamic restructuring of Cu active sites during low-temperature methanol steam reforming. Under illumination, the thermally deactivated Cu/TiO2 undergoes structural restoration from inoperative Cu2O to the originally active metallic Cu caused by photoexcited charge carriers from TiO2, thereby leading to substantially enhanced activity and stability. Given the low-intensity solar irradiation, the optimized Cu/TiO2 displays a H2 production rate of 1724.1 µmol g-1 min-1, outperforming most of the conventional photocatalytic and thermocatalytic processes. Taking advantages of the strong light-matter-reactant interaction, we achieve in situ manipulation of the Cu active sites, suggesting the feasibility for real-time functionalization of catalysts.

Engineering Heterogeneous NiS2 /NiS Cocatalysts with Progressive Electron Transfer from Planar p-Si Photocathodes for Solar Hydrogen Evolution.

The sluggish transfer of electrons from a planar p-type Si (p-Si) semiconductor to a cocatalyst restricts the activity of photoelectrochemical (PEC) hydrogen evolution. To overcome such inefficiency, an elegant interphase of the semiconductor/cocatalyst is generally necessary. Hence, in this work, a NiS2 /NiS heterojunction (NNH) is prepared in situ and applied to a planar p-Si substrate as a cocatalyst to achieve progressive electron transfer. The NNH/Si photocathode exhibits an onset potential of +0.28 V versus reversible hydrogen electrode (VRHE ) and a photocurrent density of 18.9 mA·cm-2 at 0 VRHE , as well as a 0.9% half-cell solar-to-hydrogen efficiency, which is much superior compared with those of NiS2 /Si and NiS/Si photocathodes. The enhanced performance for NNH/Si is attributed to the contact between the sectional n-type semiconducting NNH and the planar p-Si semiconductor through a p-Si/n-NiS/n-NiS2 manner that functions as a local pn-junction to promote electron transfer. Thus, the photogenerated electron is transferred from p-Si to n-NiS within NNH as the progressive medium, followed by to Ni2+ and/or S2 2- of the defect-rich n-NiS2 phase as the key active sites. This systematic work may pave the way for planar Si-based PEC applications of heterogeneous metal sulfide cocatalysts through the progressive transfer of electrons.

Triggering Water and Methanol Activation for Solar-Driven H2 Production: Interplay of Dual Active Sites over Plasmonic ZnCu Alloy.

Methanol steam reforming (MSR) is a promising reaction that enables efficient production and safe transportation of hydrogen, but it requires a relatively high temperature to achieve high activity, leading to large energy consumption. Here, we report a plasmonic ZnCu alloy catalyst, consisting of plasmonic Cu nanoparticles with surface-deposited Zn atoms, for efficient solar-driven MSR without additional thermal energy input. Experimental results and theoretical calculations suggest that Zn atoms act not only as the catalytic sites for water reduction with lower activation energy but also as the charge transfer channel, pumping hot electrons into water molecules and subsequently resulting in the formation of electron-deficient Cu for methanol activation. These merits together with photothermal heating render the optimal ZnCu catalyst a high H2 production rate of 328 mmol gcatalyst-1 h-1 with a solar energy conversion efficiency of 1.2% under 7.9 Suns irradiation, far exceeding the reported conventional photocatalytic and thermocatalytic MSR. This work provides a potential strategy for efficient solar-driven H2 production and various other energy-demanding industrial reactions through designing alloy catalysts.

Plasmonic photothermal catalysis for solar-to-fuel conversion: current status and prospects.

Solar-to-fuel conversion through photocatalytic processes is regarded as promising technology with the potential to reduce reliance on dwindling reserves of fossil fuels and to support the sustainable development of our society. However, conventional semiconductor-based photocatalytic systems suffer from unsatisfactory reaction efficiencies due to limited light harvesting abilities. Recent pioneering work from several groups, including ours, has demonstrated that visible and infrared light can be utilized by plasmonic catalysts not only to induce local heating but also to generate energetic hot carriers for initiating surface catalytic reactions and/or modulating the reaction pathways, resulting in synergistically promoted solar-to-fuel conversion efficiencies. In this perspective, we focus primarily on plasmon-mediated catalysis for thermodynamically uphill reactions converting CO2 and/or H2O into value-added products. We first introduce two types of mechanism and their applications by which reactions on plasmonic nanostructures can be initiated: either by photo-induced hot carriers (plasmonic photocatalysis) or by light-excited phonons (photothermal catalysis). Then, we emphasize examples where the hot carriers and phonon modes act in concert to contribute to the reaction (plasmonic photothermal catalysis), with special attention given to the design concepts and reaction mechanisms of the catalysts. We discuss challenges and future opportunities relating to plasmonic photothermal processes, aiming to promote an understanding of underlying mechanisms and provide guidelines for the rational design and construction of plasmonic catalysts for highly efficient solar-to-fuel conversion.

Highly efficient degradation of trichloroethylene in groundwater based on peroxymonosulfate activation by bentonite supported Fe/Ni bimetallic nanoparticle.

Advanced oxidation processes (AOPs) are promising environmental remediation technologies for in-situ groundwater treatment. In this study, a bentonite supported Fe/Ni bimetallic nanoparticle (BNF) was fabricated for peroxymonosulfate (PMS) activation. The resultant BNF exhibited high catalytic activity for trichloroethylene (TCE) degradation in weak alkaline conditions. The conditions optimal for this activity were assessed in terms of peroxygen type and BNF/PMS dosage ratios. Complete degradation of 0.1 mM TCE was achieved in 25 min at pH = 8.2 when BNF was present at 1 g/L and PMS at 5 mM concentrations. Analysis of the underlying mechanisms indicated that SO4- has a dominant role whereas OH was rather trivial. The enhancement of catalytic activity was attributed to the strong oxidization of SO4-, dispersion of Fe/Ni nanoparticles and synergistic effects between Fe and Ni. The effects of inorganic anions, pH and temperature on the BNF/PMS activity were also investigated. Cl- and NO3- has little effect on TCE degradation, while PO43- and HPO42- were inhibitory. Higher temperatures favored PMS activation and BNF/PMS exhibited good catalytic activity across a wide range of solution pH. The results indicate that a novel BNF/PMS system holds promise as a superior AOP to remediate emerging organic pollutants in groundwater.

Correction: Bismuth oxyiodide coupled with bismuth nanodots for enhanced photocatalytic bisphenol A degradation: synergistic effects and mechanistic insight.

Correction for 'Bismuth oxyiodide coupled with bismuth nanodots for enhanced photocatalytic bisphenol A degradation: synergistic effects and mechanistic insight' by Shunqin Luo et al., Nanoscale, 2017, DOI: 10.1039/c7nr05320g.

Bismuth oxyiodide coupled with bismuth nanodots for enhanced photocatalytic bisphenol A degradation: synergistic effects and mechanistic insight.

Bismuth based semiconductor photocatalysts are being generated as promising materials for photocatalysis. In this work, hydrothermal methods have been utilized to synthesize a bismuth oxyiodide semiconductor with deposited Bi nanodots (Bi-BiOI), which could create oxygen defects and accelerate photoinduced charge migration simultaneously. The resulting Bi-BiOI strongly demonstrates the high photocatalytic performance for bisphenol A and methylene blue degradation under visible light. 86% of BPA was degraded after an irradiation time of 4 hours. Electrospray ionization mass spectrometry was employed to detect the evolution of intermediates formed during the decomposition process of bisphenol A, and the following results suggested complete bisphenol A mineralization. Additionally, electron paramagnetic resonance results revealed the production of free radicals and the presence of oxygen vacancies. Furthermore, a distinctively increased photocurrent response and photoluminescence decay dynamics demonstrate that the interface between the Bi nanodots and BiOI semiconductor promotes the separation and migration of photoinduced electron-hole pairs. The lower valence band value (2.57 eV) of Bi-BiOI presented a higher oxidation potential, thus the production of hydroxyl radicals could be promoted considerably. Based on the experimental results, factors such as oxygen vacancies, effective charge migration, suppressed photoinduced electron-hole pair recombination and a high Bi-BiOI oxidation potential would result in advanced free radical production capacity, thereby enhancing the photocatalytic efficiency. The findings of our work will contribute to the fabrication of metal nanodot deposited semiconductor photocatalysts and pave the way for the utilization of advanced oxidation technology.