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The self-powered and ultra-broadband photodetectors based on photothermoelectric (PTE) effect are promising for diverse applications such as sensing, environmental monitoring, night vision and astronomy. The sensitivity of PTE photodetectors is determined by the Seebeck coefficient and the rising temperature under illumination. Previous PTE photodetectors mostly rely on traditional thermoelectric materials with Seebeck coefficients in the range of 100 μV K −1 , and array structures with multiple units are usually employed to enhance the photodetection performance. Herein, we demonstrate a reduced SrTiO 3 (r-STO) based PTE photodetector with sensitivity up to 1.2 V W −1 and broadband spectral response from 325 nm to 10.67 μm. The high performance of r-STO PTE photodetector is attributed to its intrinsic high Seebeck coefficient and phonon-enhanced photoresponse in the long wavelength infrared region. Our results open up a new avenue towards searching for novel PTE materials beyond traditional thermoelectric materials for low-cost and high-performance photodetector at room temperature. Broadband photodetectors for various applications are in high demand, however, often suffering from non-linearities at high power densities. Here, a reduced strontium titanate based photodetector exhibiting linear response up to 1235 W/cm 2 is presented not achieved by other broadband photodetectors.

Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces.

Metal nanoparticles anchored on perovskite through in situ exsolution under reducing atmosphere provide catalytically active metal/oxide interfaces for CO 2 electrolysis in solid oxide electrolysis cell. However, there are critical challenges to obtain abundant metal/oxide interfaces due to the sluggish diffusion process of dopant cations inside the bulk perovskite. Herein, we propose a strategy to promote exsolution of RuFe alloy nanoparticles on Sr 2 Fe 1.4 Ru 0.1 Mo 0.5 O 6− δ perovskite by enriching the active Ru underneath the perovskite surface via repeated redox manipulations. In situ scanning transmission electron microscopy demonstrates the dynamic structure evolution of Sr 2 Fe 1.4 Ru 0.1 Mo 0.5 O 6− δ perovskite under reducing and oxidizing atmosphere, as well as the facilitated CO 2 adsorption at RuFe@Sr 2 Fe 1.4 Ru 0.1 Mo 0.5 O 6− δ interfaces. Solid oxide electrolysis cell with RuFe@Sr 2 Fe 1.4 Ru 0.1 Mo 0.5 O 6− δ interfaces shows over 74.6% enhancement in current density of CO 2 electrolysis compared to that with Sr 2 Fe 1.4 Ru 0.1 Mo 0.5 O 6− δ counterpart as well as impressive stability for 1000 h at 1.2 V and 800 °C. Metal nanoparticles anchored on perovskite provide catalytically active interfaces for CO2 electrolysis. The authors promote exsolution of RuFe alloy nanoparticles on Sr2Fe1.4Ru0.1Mo0.5 O6−δ perovskite by enriching the active Ru underneath the perovskite surface via repeated redox manipulations.

Achieving CO oxidation at room temperature is significant for gas purification but still challenging nowadays. Pt promoted by 3 d transition metals (TMs) is a promising candidate for this reaction, but TMs are prone to be deeply oxidized in an oxygen-rich atmosphere, leading to low activity. Herein we report a unique structure design of graphene-isolated Pt from CoNi nanoparticles (PtǀCoNi) for efficiently catalytic CO oxidation in an oxygen-rich atmosphere. CoNi alloy is protected by ultrathin graphene shell from oxidation and therefore modulates the electronic property of Pt-graphene interface via electron penetration effect. This catalyst can achieve near 100% CO conversion at room temperature, while there are limited conversions over Pt/C and Pt/CoNiO x catalysts. Experiments and theoretical calculations indicate that CO will saturate Pt sites, but O 2 can adsorb at the Pt-graphene interface without competing with CO, which facilitate the O 2 activation and the subsequent surface reaction. This graphene-isolated system is distinct from the classical metal-metal oxide interface for catalysis, and it provides a new thought for the design of heterogeneous catalysts. Achieving CO oxidation at room temperature is significant for gas purification but remains challenging to perform. Here, the authors report design of graphene-isolated Pt from cobalt-nickel nanoparticles for efficiently catalytic CO oxidation in an oxygen-rich atmosphere.

Oxidative dispersion has been widely used in regeneration of sintered metal catalysts and fabrication of single atom catalysts, which is attributed to an oxidation-induced dispersion mechanism. However, the interplay of gas-metal-support interaction in the dispersion processes, especially the gas-metal interaction has not been well illustrated. Here, we show dynamic dispersion of silver nanostructures on silicon nitride surface under reducing/oxidizing conditions and during carbon monoxide oxidation reaction. Utilizing environmental scanning (transmission) electron microscopy and near-ambient pressure photoelectron spectroscopy/photoemission electron microscopy, we unravel a new adsorption-induced dispersion mechanism in such a typical oxidative dispersion process. The strong gas-metal interaction achieved by chemisorption of oxygen on nearly-metallic silver nanoclusters is the internal driving force for dispersion. In situ observations show that the dispersed nearly-metallic silver nanoclusters are oxidized upon cooling in oxygen atmosphere, which could mislead to the understanding of oxidation-induced dispersion. We further understand the oxidative dispersion mechanism from the view of dynamic equilibrium taking temperature and gas pressure into account, which should be applied to many other metals such as gold, copper, palladium, etc. and other reaction conditions. Designing ultra small metal nanoclusters or single atoms with metallic state is a challenge. Here, the authors demonstrate the stabilization of ultra small silver clusters in the nearly-metallic state by oxygen adsorption at high temperature, using in situ spectroscopy and microscope technologies.

Renewable energy-driven electrocatalytic nitrate reduction reaction presents a low-carbon and sustainable route for ammonia synthesis under mild conditions. Yet, the practical application of this process is currently hindered by unsatisfactory electrocatalytic activity and long-term stability. Herein we achieve high-rate ammonia electrosynthesis using a stable amorphous/crystalline dual-phase Cu catalyst. The ammonia partial current density and formation rate reach 3.33 ± 0.005 A cm −2 and 15.5 ± 0.02 mmol h −1  cm −2 at a low cell voltage of 2.6 ± 0.01 V, respectively. Remarkably, the dual-phase Cu catalyst can maintain stable ammonia production with a Faradaic efficiency of around 90% at a high current density of 1.5 A cm −2 for up to 300 h. A scale-up demonstration with an electrode size of 100 cm 2 achieves an ammonia formation rate as high as 11.9 ± 0.5 g h −1 at a total current of 160 A. The impressive electrocatalytic performance is ascribed to the presence of stable amorphous Cu domains which promote the adsorption and hydrogenation of nitrogen-containing intermediates, thus improving reaction kinetics for ammonia formation. This work underscores the importance of stabilizing metastable amorphous structures for improving electrocatalytic reactivity and long-term stability. The authors develop an efficient and stable amorphous/crystalline dual-phase Cu catalyst towards electrocatalytic nitrate reduction reaction, with an ammonia Faradaic efficiency of around 90% at a high current density of 1.5 A cm −2 for up to 300 h.

Significant progress has been demonstrated in the development of bifunctional oxide-zeolite catalyst concept to tackle the selectivity challenge in syngas chemistry. Despite general recognition on the importance of defect sites of metal oxides for CO/H 2 activation, the actual structure and catalytic roles are far from being well understood. We demonstrate here that syngas conversion can be steered along a highly active and selective pathway towards light olefins via ketene-acetate (acetyl) intermediates by the surface with coordination unsaturated metal species, oxygen vacancies and zinc vacancies over ZnGaO x spinel−SAPO-34 composites. It gives 75.6% light-olefins selectivity and 49.5% CO conversion. By contrast, spinel−SAPO-34 containing only a small amount of oxygen vacancies and zinc vacancies gives only 14.9% light olefins selectivity at 6.6% CO conversion under the same condition. These findings reveal the importance to tailor the structure of metal oxides with coordination unsaturated metal sites/oxygen vacancies in selectivity control within the oxide-zeolite framework for syngas conversion and being anticipated also for CO 2 hydrogenation. Great progress has been made in the development of bifunctional oxide-zeolite catalysts to tackle the selectivity challenge in syngas chemistry. Here the authors show syngas conversion can be steered along a highly active and selective pathway towards light olefins via ketene acetate (acetyl) intermediates.

Geometric or electronic confinement of guests inside nanoporous hosts promises to deliver unusual catalytic or opto-electronic functionality from existing materials but is challenging to obtain particularly using metastable hosts, such as metal–organic frameworks (MOFs). Reagents (e.g. precursor) may be too large for impregnation and synthesis conditions may also destroy the hosts. Here we use thermodynamic Pourbaix diagrams (favorable redox and pH conditions) to describe a general method for metal-compound guest synthesis by rationally selecting reaction agents and conditions. Specifically we demonstrate a MOF-confined RuO 2 catalyst (RuO 2 @MOF-808-P) with exceptionally high catalytic CO oxidation below 150 °C as compared to the conventionally made SiO 2 -supported RuO 2 (RuO 2 /SiO 2 ). This can be caused by weaker interactions between CO/O and the MOF-encapsulated RuO 2 surface thus avoiding adsorption-induced catalytic surface passivation. We further describe applications of the Pourbaix-enabled guest synthesis (PEGS) strategy with tutorial examples for the general synthesis of arbitrary guests (e.g. metals, oxides, hydroxides, sulfides). Loading guests inside the pre-existing pores of nanoporous hosts remains challenging. Here, the authors introduce a rational route for incorporation of guest compounds into an arbitrary nanoporous host, enabling the investigation of multiple host-guest systems with surprising functionalities.

In heterogeneous catalysis catalyst activation is often observed during the reaction process, which is mostly attributed to the induction by reactants. In this work we report that surface structure of molybdenum nitride (MoN x ) catalyst exhibits a high dependency on the partial pressure or concentration of reaction products i.e., CO and H 2 O in reverse water gas-shift reaction (RWGS) (CO 2 :H 2  = 1:3) but not reactants of CO 2 and H 2 . Molybdenum oxide (MoO x ) overlayers formed by oxidation with H 2 O are observed at reaction pressure below 10 mbar or with low partial pressure of CO/H 2 O products, while CO-induced surface carbonization happens at reaction pressure above 100 mbar and with high partial pressure of CO/H 2 O products. The reaction products induce restructuring of MoN x surface into more active molybdenum carbide (MoC x ) to increase the reaction rate and make for higher partial pressure CO, which in turn promote further surface carbonization of MoN x . We refer to this as the positive feedback between catalytic activity and catalyst activation in RWGS, which should be widely present in heterogeneous catalysis. Catalyst activation commonly occurs during reactions. This study demonstrates that the surface’s active structure in nitride catalysts during the reverse water gas-shift reaction varies with the partial pressure of reaction products, resulting in enhanced catalytic activity through positive feedback between catalytic activity and the evolution of MoNx’s active structure.

Hydrogen production through water splitting has been considered as a green, pure and high-efficient technique. As an important half-reaction involved, hydrogen evolution reaction is a complex electrochemical process involving liquid-solid-gas three-phase interface behaviour. Therefore, new concepts and strategies of material design are needed to smooth each pivotal step. Here we report a multiscale structural and electronic control of molybdenum disulfide foam to synergistically promote the hydrogen evolution process. The optimized three-dimensional molybdenum disulfide foam with uniform mesopores, vertically aligned two-dimensional layers and cobalt atoms doping demonstrated a high hydrogen evolution activity and stability. In addition, density functional theory calculations indicate that molybdenum disulfide with moderate cobalt doping content possesses the optimal activity. This study demonstrates the validity of multiscale control in molybdenum disulfide via overall consideration of the mass transport, and the accessibility, quantity and capability of active sites towards electrocatalytic hydrogen evolution, which may also be extended to other energy-related processes. The hydrogen evolution reaction is a complicated process involving liquid-solid-gas three-phase interface behaviour. Here, the authors report the multiscale structural and electronic control of molybdenum disulfide foam and demonstrate its high activity and stability for hydrogen evolution.