Photochemical H dissociation for nearly quantitative CO reduction to ethylene.

Producing olefins by carbon dioxide (CO) hydrogenation is a long-standing goal. The usual products are multicarbon mixtures because the critical step of heterolytic hydrogen (H) dissociation at high temperatures complicates selectivity control. In this study, we report that irradiating gold-titanium dioxide at 365 nanometers induces heterolytic H dissociation at ambient temperature.

Revealing Effect of Surface Hydroxyl Variation on Charge Spatiotemporal Dynamics in Photocatalysis.

Oxide semiconductor photocatalysts are widely used for solar energy conversion, and the abundant intrinsic hydroxyl groups as defect sites on their surfaces play a key role in photocatalytic performance. However, the nature of surface hydroxyl-related defect states and their effect on the behavior of photogenerated charges, especially if targeted for charge separation, and whether the electrons and holes facing these hydroxyl sites in the same temporal and spatial ranges compete and conflict are unknown. Understanding these may help us to reasonably control defect-induced charge separation.

Efficient Light-Driven Ion Pumping for Deep Desalination via the Vertical Gradient Protonation of Covalent Organic Framework Membranes.

Traditional desalination methods face criticism due to high energy requirements and inadequate trace ion removal, whereas natural light-driven ion pumps offer superior efficiency. Current synthetic systems are constrained by short exciton lifetimes, which limit their ability to generate sufficient electric fields for effective ion pumping. We introduce an innovative approach utilizing covalent-organic framework membranes that enhance light absorption and reduce charge recombination through vertical gradient protonation of imine linkages during acid-catalyzed liquid-liquid interfacial polymerization.

An Artificial Leaf with Patterned Photocatalysts for Sunlight-Driven Water Splitting.

Plant leaves can turn entirely absorbed light into chemical energy due to their spatially separated photosystems I and II in the thylakoid membrane that enables unidirectional Z-scheme type charge transfer between them. In artificial systems that mimic leaves, a lack of spatial and interfacial control of active units (i.e.

Surface photovoltage microscopy for mapping charge separation on photocatalyst particles.

Solar-driven photocatalytic reactions offer a promising route to clean and sustainable energy, and the spatial separation of photogenerated charges on the photocatalyst surface is the key to determining photocatalytic efficiency. However, probing the charge-separation properties of photocatalysts is a formidable challenge because of the spatially heterogeneous microstructures, complicated charge-separation mechanisms and lack of sensitivity for detecting the low density of separated photogenerated charges. Recently, we developed surface photovoltage microscopy (SPVM) with high spatial and energy resolution that enables the direct mapping of surface-charge distributions and quantitative assessment of the charge-separation properties of photocatalysts at the nanoscale, potentially providing unprecedented insights into photocatalytic charge-separation processes.

Bioinspired carbon nanotube-based nanofluidic ionic transistor with ultrahigh switching capabilities for logic circuits.

The voltage-gated ion channels, also known as ionic transistors, play substantial roles in biological systems and ion-ion selective separation. However, implementing the ultrafast switchable capabilities and polarity switching of ionic transistors remains a challenge. Here, we report a nanofluidic ionic transistor based on carbon nanotubes, which exhibits an on/off ratio of 10 at operational gate voltage as low as 1 V.

Liquid metal-embraced photoactive films for artificial photosynthesis.

The practical applications of solar-driven water splitting pivot on significant advances that enable scalable production of robust photoactive films. Here, we propose a proof-of-concept for fabricating robust photoactive films by a particle-implanting technique (PiP) which embeds semiconductor photoabsorbers in the liquid metal. The strong semiconductor/metal interaction enables resulting films efficient collection of photogenerated charges and superior photoactivity.

Visualizing the role of applied voltage in non-metal electrocatalysts.

Understanding how applied voltage drives the electrocatalytic reaction at the nanoscale is a fundamental scientific problem, particularly in non-metallic electrocatalysts, due to their low intrinsic carrier concentration. Herein, using monolayer molybdenum disulfide (MoS) as a model system of non-metallic catalyst, the potential drops across the basal plane of MoS (ΔV) and the electric double layer (ΔV) are decoupled quantitatively as a function of applied voltage through surface potential microscopy. We visualize the evolution of the band structure under liquid conditions and clarify the process of E keeping moving deep into E, revealing the formation process of the electrolyte gating effect.

Achieving High Selectivity in Photocatalytic Oxidation of Toluene on Amorphous BiOCl Nanosheets Coupled with TiO.

The inert C()-H bond and easy overoxidation of toluene make the selective oxidation of toluene to benzaldehyde a great challenge. Herein, we present that a photocatalyst, constructed with a small amount (1 mol %) of amorphous BiOCl nanosheets assembled on TiO (denoted as 0.01BOC/TiO), shows excellent performance in toluene oxidation to benzaldehyde, with 85% selectivity at 10% conversion, and the benzaldehyde formation rate is up to 1.

Selective Exposure of Robust Perovskite Layer of Aurivillius-Type Compounds for Stable Photocatalytic Overall Water Splitting.

Aurivillius-type compounds ((Bi O ) (A B O ) ) with alternately stacked layers of bismuth oxide (Bi O ) and perovskite (A B O ) are promising photocatalysts for overall water splitting due to their suitable band structures and adjustable layered characteristics. However, the self-reduction of Bi at the top (Bi O ) layers induced by photogenerated electrons during photocatalytic processes causes inactivation of the compounds as photocatalysts. Here, using Bi TiNbO as a model photocatalyst, its surface termination is modulated by acid etching, which well suppresses the self-corrosion phenomenon.

Graphene Mediates Charge Transfer between Lead Chromate and a Cobalt Cubane Cocatalyst for Photocatalytic Water Oxidation.

The interfacial barrier of charge transfer from semiconductors to cocatalysts means that the photogenerated charges cannot be fully utilized, especially for the challenging water oxidation reaction. Using cobalt cubane molecules (Co O ) as water oxidation cocatalysts, we rationally assembled partially oxidized graphene (pGO), acting as a charge-transfer mediator, on the hole-accumulating {-101} facets of lead chromate (PbCrO ) crystal. The assembled pGO enables preferable immobilization of Co O molecules on the {-101} facets of the PbCrO crystal, which is favorable for the photogenerated holes transferring from PbCrO to Co O molecules.

Linking the Photoinduced Surface Potential Difference to Interfacial Charge Transfer in Photoelectrocatalytic Water Oxidation.

Charge transfer at the semiconductor/solution interface is fundamental to photoelectrocatalytic water splitting. Although insights into charge transfer in the electrocatalytic process can be gained from the phenomenological Butler-Volmer theory, there is limited understanding of interfacial charge transfer in the photoelectrocatalytic process, which involves intricate effects of light, bias, and catalysis. Here, using operando surface potential measurements, we decouple the charge transfer and surface reaction processes and find that the surface reaction enhances the photovoltage via a reaction-related photoinduced charge transfer regime as demonstrated on a SrTiO photoanode.

Spatiotemporal imaging of charge transfer in photocatalyst particles.

The water-splitting reaction using photocatalyst particles is a promising route for solar fuel production. Photo-induced charge transfer from a photocatalyst to catalytic surface sites is key in ensuring photocatalytic efficiency; however, it is challenging to understand this process, which spans a wide spatiotemporal range from nanometres to micrometres and from femtoseconds to seconds. Although the steady-state charge distribution on single photocatalyst particles has been mapped by microscopic techniques, and the charge transfer dynamics in photocatalyst aggregations have been revealed by time-resolved spectroscopy, spatiotemporally evolving charge transfer processes in single photocatalyst particles cannot be tracked, and their exact mechanism is unknown.

Bipolar charge collecting structure enables overall water splitting on ferroelectric photocatalysts.

Ferroelectrics are considered excellent photocatalytic candidates for solar fuel production because of the unidirectional charge separation and above-gap photovoltage. Nevertheless, the performance of ferroelectric photocatalysts is often moderate. A few studies showed that these types of photocatalysts could achieve overall water splitting.

Tuning the Anisotropic Facet of Lead Chromate Photocatalysts to Promote Spatial Charge Separation.

A crucial issue in artificial photosynthesis is how to modulate the behaviors of photogenerated charges of semiconductor photocatalysts. Here, using lead chromate (PbCrO ) as an example, we conducted the morphology tailoring from parallelepiped (p-PbCrO ) to truncated decahedron (t-PbCrO ) and elongated rhombic (r-PbCrO ), resulting in exposed anisotropic facets. The spatial separation of photogenerated charges closely correlates to the anisotropic facets of crystals, which can only be realized for t-PbCrO and r-PbCrO .

Constructing Anatase-Brookite TiO Phase Junction by Thermal Topotactic Transition to Promote Charge Separation for Superior Photocatalytic H Generation.

Phase junctions of photocatalysts can promote the separation of photogenerated charge carriers for efficient utilization of the carriers. Construction of phase junctions and establishing their structure-performance relationship are still required. Herein, polycrystalline TiO decahedral plates with different phases were synthesized by thermal treatment-induced topotactic transition of titanium oxalate crystals.

Unraveling Charge-Separation Mechanisms in Photocatalyst Particles by Spatially Resolved Surface Photovoltage Techniques.

The photocatalytic conversion of solar energy offers a potential route to renewable energy, and its efficiency relies on effective charge separation in nanostructured photocatalysts. Understanding the charge-separation mechanism is key to improving the photocatalytic performance and this has now been enabled by advances in the spatially resolved surface photovoltage (SRSPV) method. In this Review we highlight progress made by SRSPV in mapping charge distributions at the nanoscale and determining the driving forces of charge separation in heterogeneous photocatalyst particles.

Identifying the Role of the Local Charge Density on the Hydrogen Evolution Reaction of the Photoelectrode.

Understanding the role of surface charges in the catalytic reaction is of great importance to fundamental science in photoelectrochemistry (PEC). However, spatial heterogeneities of charge transfer sites and catalytic sites at the electrode/electrolyte interface obscures the surface reaction process. Herein, we quantified the relationship between the local catalytic current of the hydrogen evolution reaction (HER) and the surface charge density using spatially resolved photovoltage microscopy on the Pt/Ti array on the p-Si photoelectrode.

Light-driven directional ion transport for enhanced osmotic energy harvesting.

Light-driven ion (proton) transport is a crucial process both for photosynthesis of green plants and solar energy harvesting of some archaea. Here, we describe use of a TiO/CN semiconductor heterojunction nanotube membrane to realize similar light-driven directional ion transport performance to that of biological systems. This heterojunction system can be fabricated by two simple deposition steps.

Visualizing the Spatial Heterogeneity of Electron Transfer on a Metallic Nanoplate Prism.

The involvement between electron transfer (ET) and catalytic reaction at the electrocatalyst surface makes the electrochemical process challenging to understand and control. Even ET process, a primary step, is still ambiguous because it is unclear how the ET process is related to the nanostructured electrocatalyst. Herein, locally enhanced ET current dominated by mass transport effect at corner and edge sites bounded by {111} facets on single Au triangular nanoplates was clearly imaged.

Nanospatial Charge Modulation of Monodispersed Polymeric Microsphere Photocatalysts for Exceptional Hydrogen Peroxide Production.

Photocatalysis offers a sustainable strategy for hydrogen peroxide (H O ) production, which is an essential oxidant and emerging energy carrier in modern chemical industry. The development of polymer-based photocatalysts to produce H O has great potential but is limited by lower efficiency due to the limitation of light utilization and the low charge separation efficiency. Herein, a series of monodispersed mesoporous resorcinol-formaldehyde resin spheres (MRFS) are reported with a rational designed spatial charge distribution, exhibiting wide light absorption with a solar-to-chemical conversion (SCC) efficiency of 1.

Probing of coupling effect induced plasmonic charge accumulation for water oxidation.

A key issue for redox reactions in plasmon-induced photocatalysis, particularly for water oxidation, is the concentration of surface-accumulating charges (electrons or holes) at a reaction site for artificial photosynthesis. However, where plasmonic charge accumulated at a catalyst's surface, and how to improve local charge density at active sites, remains unknown because it is difficult to identify the exact spatial location and local density of the plasmon-induced charge, particularly with regard to holes. Herein, we show that at the single particle level, plasmon-coupling-induced holes can be greatly accumulated at the plasmonic Au nanoparticle dimer/TiO interface in the nanogap region, as directly evidenced by the locally enhanced surface photovoltage.

Internal-Field-Enhanced Charge Separation in a Single-Domain Ferroelectric PbTiO Photocatalyst.

Ferroelectric materials with spontaneous polarization-induced internal electric fields have drawn increasing attention in solar fuel production due to the intrinsic polarized structure. However, the origination of charge separation in these materials at the nano/microlevel is ambiguous owing to the complexity of the multielectric fields. Besides, the observed charge separation ability is far from theoretical expectation.

Unraveling the Kinetics of Photocatalytic Water Oxidation on WO.

Understanding the reaction kinetics of photocatalytic water splitting is important for the solar energy conversion field. Particularly, identifying the main obstacle in solar water oxidation is intriguing for efforts to promote the energy conversion efficiency. Herein, we take WO and cesium treated WO as prototypical models to disclose the reaction kinetics of photocatalytic water oxidation and found that the lack of long-lived surface holes is the bottleneck in the photocatalytic process.