Photothermal Catalyst Research Articles

Light-Off in Plasmon-Mediated Photocatalysis.

In plasmon-mediated photocatalysis it is of critical importance to differentiate light-induced catalytic reaction rate enhancement channels, which include near-field effects, direct hot carrier injection, and photothermal catalyst heating. In particular, the discrimination of photothermal and hot electron channels is experimentally challenging, and their role is under keen debate. Here we demonstrate using the example of CO oxidation over nanofabricated neat Pd and Au50Pd50 alloy catalysts, how photothermal rate enhancement differs by up to 3 orders of magnitude for the same photon flux, and how this effect is controlled solely by the position of catalyst operation along the light-off curve measured in the dark. This highlights that small fluctuations in reactor temperature or temperature gradients across a sample may dramatically impact global and local photothermal rate enhancement, respectively, and thus control both the balance between different rate enhancement mechanisms and the way strategies to efficiently distinguish between them should be devised.

Cobalt‐Sputtered Anodic Aluminum Oxide Membrane for Efficient Photothermal CO2 Hydrogenation

AbstractThe rational design of nanoarray‐structured catalysts is an accessible way to increase light absorption ability and boost photothermal CO2 conversion efficiency. However, practical application of current nanoarrays is hindered by complex synthesis procedures, high costs, and low catalyst yields. Herein, we report a simple, robust method to prepare efficient photothermal catalyst by sputtering Co nanoparticles on commercial anodic aluminum oxide (AAO) membrane. The detailed study shows that gas diffusion and catalytic activity can be affected by AAO structures, such as channel size and shape. The optimized Co@dpAAO catalyst reached a record Co‐based photothermal CO2 conversion rate of 1666 mmol ⋅ gCo−1 ⋅ h−1. This study not only provides a facile way to synthesize efficient catalysts, but also promotes the understanding of constructing nanoarray‐based photothermal catalysts.

Solar-driven hydrogen production from steam methane reforming using highly dispersed metallic Ni catalysts supported on layered double hydroxide nanosheets

Hydrogen (H2) is an indispensable and significant raw material in chemical engineering. Because 50% of all H2 production comes from steam methane reforming (SRM), the high energy inputs and reaction temperatures required by this process cannot be ignored. These issues have motivated research on methods to achieve a sustainable process to active methane (CH4) for H2 production. In this work, a photothermal catalyst composed of highly dispersed metallic Ni supported by layered double hydroxide nanosheets showed outstanding SRM performance, with a H2 evolution rate of 388.28 μmol·g−1·min−1. Under solar irradiation, a H2 evolution rate of 668.76 μmol·g−1·min−1 could be obtained. These results provide a new perspective for the direct use of solar energy to produce H2 from natural gas and water.

Efficient degradation of tetracycline by RGO@black titanium dioxide nanofluid via enhanced catalysis and photothermal conversion

The applications of photocatalytic pollutant degradation have remained limited due to the low efficiency of solar energy utilization. In this study, a photothermal catalyst consisting of reduced graphene oxide @ black TiO2 (RGO@BT) nanofluid with effective full-spectrum (from ultraviolet to infrared light) absorption was synthesized by a typical two-step method of high temperature calcination and hydrothermal method. Moreover, the photothermal catalytic performance of the RGO@BT nanofluid on tetracycline was verified. Compared with individual processes (i.e, photocatalysis and thermocatalysis), the photothermal catalytic process significantly enhanced tetracycline degradation under simulated global standard spectrum sunlight (AM 1.5G, 1000 W m−2). The maximum photothermal conversion efficiency reached 91.8%, which resulted in 94.7% tetracycline degradation (40 mg L−1) after 120 min of treatment with 200 mg L−1 RGO@BT nanofluid. Holes, OH, and O2− were found to be the main active species during the photothermal catalytic process. Moreover, heat was spontaneously converted from light energy without the use of any external energy source. The elevated system temperature facilitated the tetracycline degradation based on the Arrhenius behavior. These findings provide insights into the improvement of photocatalytic efficiency in organic contaminant degradation via solar energy-efficient photothermal conversion materials.

Construction of a ternary spatial junction in yolk–shell nanoreactor for efficient photo-thermal catalytic hydrogen generation

Highly efficient solar‐to‐hydrogen (H2) conversion depends crucially on the light-harvesting capability, cumulative cascade efficiency of photo-induced carriers, and surficial vibrant kinetics of photocatalysts. Herein, a spatially ternary carbon nanospheres@TiO2/reduced TiO2 (denoted as C@TiO2/TiO2-x) yolk–shell (YS) nanoreactor is proposed as a model solar water splitting system, in which an excellent photothermal conversion is achieved by the YS nanoreactor with carbon core as the nanoheater and its light absorption range is extended to the longer wavelength of even near‐infrared light. Spatial inside-out junctions in the nanoreactor were designed to frame multiple-level charge transfers with the Ti–O–C channel as charge transport bridge. Surface oxygen vacancy defects (OVs) induced by Ti3+ self-doping accelerate the mass transfer, trap the photo-induced electrons, and afford the active sites for proton reduction. Therefore, benefiting from the dual contributions of the heat built-up and ternary spatial junctions in the C@TiO2/TiO2-x YS nanoreactor, its photo-thermal catalytic H2 conversion activity (3667 μmol h−1 g−1) has been remarkably enhanced at least 22-fold under simulated sunlight irradiation (AM 1.5G) without the use of noble metal cocatalysts. This YS spatial junction construction strategy for cascade electron transfer in nanoreactors may be further applied to other photo-thermal catalysts for enhanced solar-to-fuel conversions.

A Photothermal Catalyst Consisting of Manganese Oxide Clusters and Antimony-doped Tin Oxide Nanocrystal: Application to Environmental Purification

Manganese oxide clusters were formed on SnO2 (MnOx/SnO2) and antimony-doped SnO2 (MnOx/ATO) nanocrystals by impregnation. MnOx/ATO possesses strong and broad absorption due to the localized surface plasmon resonance of ATO nanocrystals in the near infrared region. The catalytic activity was studied for degradation of 2-naphthol used as a model pollutant in hydrosphere. Irradiation of near infrared light to MnOx/ATO causes a drastic increase in the activity, whereas the effect is slight in the MnOx/SnO2 system.

A core-shell catalyst design boosts the performance of photothermal reverse water gas shift catalysis

Photothermal reverse water gas shift (RWGS) catalysis holds promise for efficient conversions of greenhouse gas CO2 and renewable H2, powered solely by sunlight, into CO, an important feedstock for the chemical industry. However, the performance of photothermal RWGS catalysis over existing supported catalysts is limited by the balance between the catalyst loading and dispersity, as well as stability against sintering. Herein, we report a core-shell strategy for the design of photothermal catalysts, by using Ni12P5 as an example, with simultaneously strong light absorption ability, high dispersity and stability. The core-shell structured Ni12P5@SiO2 catalyst with a relatively small Ni12P5 particle size of 15 nm at a high Ni12P5 loading of 30 wt% exhibits improved activity, nearly 100% CO selectivity, and superior stability in photothermal RWGS catalysis, particularly under intense illuminations. Our study clearly reveals the effectiveness of the core-shell strategy in breaking the limitation of supported catalysts and boosting the performance of photothermal CO2 catalysis.

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO2 under mild condition is of great importance because these reactions involving CO2 can not only produce value-added chemicals from abundant and inexpensive CO2 feedstock but also close the carbon cycle. However, the chemical inertness of CO2 requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO2. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO2 at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO2 conversion to value-added chemicals under mild condition.

Probing Activity Enhancement of Photothermal Catalyst under Near-Infrared Irradiation.

Exploring highly efficient catalysts with excellent photothermal conversion and further unveiling their catalytic mechanism are of significant importance for photothermal catalysis technologies, but there remain grand challenges to these activities. Herein, we fabricate a nest-like photothermal nanocatalyst with Pd decorated on a N-doped carbon functionalized Bi2S3 nanosphere (Bi2S3@NC@Pd). Given its well-dispersed ultrafine Pd nanoparticles and the excellent photothermal heating ability of support material, the Bi2S3@NC@Pd composite exhibits a superior activity and photothermal conversion property to commercial Pd/C catalyst for hydrogenation of organic dyes upon exposure to near-infrared (NIR) light irradiation. In addition, the photothermal effect (temperature rise) and activity enhancement of the heterogeneous catalysis system are further probed by comparing the reaction rate with and without the NIR light irradiation. Furthermore, the catalytic behaviors of the Bi2S3@NC@Pd catalyst under conventional and photothermal heating are investigated at the same reaction temperature. This work not only improves our fundamental understanding of the catalytic behavior in heterogeneous liquid-solid reaction systems under near-infrared irradiation but also may promote the design of catalysts with photothermally promoted activity.

Fabrication of Black In2O3 with Dense Oxygen Vacancy through Dual Functional Carbon Doping for Enhancing Photothermal CO2 Hydrogenation

AbstractPhotothermocatalytic CO2 reduction as the channel of the energy and environmental issues resolution has captured persistent attention in recent years. In2O3 has been prompted to be a potential photothermal catalyst in this sector on account of its unique physicochemical properties. However, different from the metal‐based photothermal catalyst with the nature of efficient light‐to‐thermal conversion and H2 dissociation, the wide‐bandgap semiconductor needs to be modified to possess wide‐wavelength‐range absorption and the active surface. It remains a challenge to achieve the two aims simultaneously via a single material modulation approach. In this study, one strategy of carbon doping can empower In2O3 with two advantageous modifications. Carbon doping can reduce the formation energy of oxygen vacancy, which induces the generation of oxygen‐vacancy‐riched material. The introduction of oxygen defect levels and carbon doping levels in the bandgap of In2O3 significantly reduces this bandgap, which endows it full‐spectral and intensive solar light absorption. Therefore, the carbon doped In2O3 achieves effective light‐to‐thermal conversion and delivers a 123.6 mmol g–1 h–1 of CO generation rate with near‐unity selectivity, as well as prominent stability in photothermocatalytic CO2 reduction.

Protein-Zn(II) networks derived N-doped porous carbon-supported ZnS for photothermally catalytic CO2 conversion

It is highly desired but remains challenging to develop efficient catalysts for CO2 conversion. Herein, N-doped porous carbon-supported ultra-small ZnS (ZnS/NPC‒X) were developed as photothermal catalysts for CO2 conversion by pyrolyzing the protein-Zn(II) network. The optimal catalyst ZnS/NPC‒2 possesses plenty of Lewis acid/base sites, hierarchical porous structure and high photothermal efficiency, jointly affording it high photothermally catalytic performance for CO2 cycloaddition and methylation reactions. This work provides a new strategy to prepare porous carbon-supported catalysts, which can find wide applications in photothermal catalysis.

Visible-light-driven prompt and quantitative production of lactic acid from biomass sugars over a N-TiO2 photothermal catalyst

Biomass sugars can be quantitatively upgraded to lactic acid in water over a visible-light-activated N-TiO2 photothermal catalyst under mild conditions (60 °C, 0.5–2 h).

Fe clusters embedded on N-doped graphene as a photothermal catalyst for selective CO2 hydrogenation.

In comparison with the Co analog, small Fe clusters incorporated in a graphene matrix exhibit a photo-assisted increase of 110% in reverse water gas shift CO2 hydrogenation under UV-Vis light irradiation. Available data indicate that the photo-assistance derives from light absorption by the N-doped graphene followed by charge recombination at the Fe clusters, increasing their local temperature.

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.

Transforming glycerol and CO2 into glycerol carbonate over La2O2CO3–ZnO catalyst — a case study of the photo-thermal synergism

La2O2CO3–ZnO was investigated as an efficient photo-thermal catalyst for transforming glycerol and CO2 into glycerol carbonate.

Photothermal catalysts for hydrogenation reactions.

Hydrogenation reactions are an important process in today's chemical industry. Typically, hydrogenation reactions involve the removal of an unsaturated bond in olefins or other polyenes via thermal catalysis using hydrogen. As hydrogenation reactions are often carried out at temperatures up to several hundred degrees, they require significant energy input which typically comes from burning fossil fuels. In order to conserve fossil fuels and reduce CO2 emissions, researchers are now developing photothermal catalysts for hydrogenation reactions, which harness concentrated sunlight to achieve the required reaction temperatures or introduce sunlight into thermal-driven reaction systems to reduce the reaction temperatures. Photothermal catalysts thus need to be able to efficiently absorb sunlight, whilst also being able to drive the desired hydrogenation reaction with high activity and selectivity. In this review, we summarize recent research aimed at the development of photothermal catalysts for CO2/CO hydrogenation and alkene/alkyne/aromatic hydrogenation. Particular emphasis is placed on uncovering the reaction mechanisms at the molecular level, which in turn guides the rational design of photothermal catalysts with better performance.

Efficient Visible‐Light Driven Photothermal Conversion of CO2 to Methane by Nickel Nanoparticles Supported on Barium Titanate

AbstractSolar‐driven methanation represents a potentially cost‐efficient and environmentally friendly route for the direct hydrogenation of CO2. Recently, photothermal catalysis, which involves the combination of both photochemical and thermochemical pathways, has emerged as a promising strategy for the production of solar fuels. For a photothermal catalyst to efficiently convert CO2 under illumination, in the absence of external heating, effective light harvesting, an excellent photothermal conversion and efficient active sites are required. Here, a new composite catalyst consisting of Ni nanoparticles supported on barium titanate that, under optimal reaction conditions, is able to hydrogenate CO2 to CH4 at nearly 100% selectivity with production rates as high as 103.7 mmol g–1 h–1 under both UV–visible and visible irradiation (production rate: 40.3 mmol g−1 h–1) is reported. Mechanistic studies suggest that reaction mostly proceeds through a nonthermal hot‐electron‐driven pathway, with a smaller thermal contribution.

Cobalt carbide nanosheets as effective catalysts toward photothermal degradation of mustard-gas simulants under solar light

Here, ultrathin cobalt carbide (Co2C) nanosheets are firstly illustrated as effective and robust catalysts toward photothermal degradation of sulfur mustard simulants (e.g., 2-chloroethyl ethyl sulfide, CEES) under solar light. Under the optimal conditions, the degradation rate of CEES by Co2C nanosheets is up to 98 %, which is much higher than the widely used P25 and anatase TiO2 nanoparticles. Moreover, the degradation performance is comparable or even better than those typical photothermal catalysts, including MnO2, MnOx-TiO2 and Co3O4, under identical conditions. Experimental evidences and density functional theory (DFT) calculations reveal that the superior activity is attributed to three main reasons: (i) the high photo-to-heat conversion efficiency of Co2C enables an elevated surface temperature for chemical bond breaking, (ii) the feasible binding of CEES on Co2C surface via CoS and CoCl coordination promotes the process of degradation, and (iii) the surface hydroxyl groups (OH) on Co2C nanosheets favor the degradation of CEES. Obviously, this work provides new insights into practical and large-scale application of transition metal carbides (TMCs) as novel photothermal catalysts in the decontamination of chemical warfare agents (CWAs) under ambient conditions (i.e., solar light and room temperature).

HI-Light: A Glass-Waveguide-Based "Shell-and-Tube" Photothermal Reactor Platform for Converting CO2 to Fuels.

SummaryIn this work, we introduce HI-Light, a surface-engineered glass-waveguide-based “shell-and-tube” type photothermal reactor which is both scalable in diameter and length. We examine the effect of temperature, light irradiation, and residence time on its photo-thermocatalytic performance for CO2 hydrogenation to form CO, with a cubic phase defect-laden indium oxide, In2O3-x(OH)y, catalyst. We demonstrate the light enhancement effect under a variety of reaction conditions. Notably, the light-on performance for the cubic nanocrystal photocatalyst exhibits a CO evolution rate at 15.40 mmol gcat−1 hr−1 at 300°C and atmospheric pressure. This is 20 times higher conversion rate per unit catalyst mass per unit time beyond previously reported In2O3-x(OH)y catalyst in the cubic form under comparable operation conditions and more than 5 times higher than that of its rhombohedral polymorph. This result underscores that improvement in photo-thermocatalytic reactor design enables uniform light distribution and better reactant/catalyst mixing, thus significantly improving catalyst utilization.

Emerging material engineering strategies for amplifying photothermal heterogeneous CO2 catalysis

A fundamental understanding of basic driving forces and the role of light in photothermal CO 2 catalysis is covered. The progress of the catalyst development and corresponding material engineering strategies are summarized. Closing the carbon loop, through CO 2 capture and utilization, is a promising route to mitigate climate change. Solar energy is a sustainable energy source which can be exploited to drive catalytic reactions for utilizing CO 2 , including converting the CO 2 into useful products. Solar energy can be harnessed through a range of different pathways to valorize CO 2 . Whilst using solar energy to drive CO 2 reduction has vast potential to promote catalytic CO 2 conversions, the progress is limited due to the lack of understanding of property-performance relations as well as feasible material engineering approaches. Herein, we outline the various driving forces involved in photothermal CO 2 catalysis. The heat from solar energy can be utilized to induce CO 2 catalytic reduction reactions via the photothermal effect. Further, solar energy can act to modify reaction pathways through light-matter interactions. Light-induced chemical functions have demonstrated the ability to regulate intermediary reaction steps, and thus control the reaction selectivity. Photothermal catalyst structures and specific catalyst design strategies are discussed in this context. This review provides a comprehensive understanding of the heat-light synergy and guidance for rational photothermal catalyst design for CO 2 utilization.