Isolated Ni Atoms Enable Near-Unity CH4 Selectivity for Photothermal CO2 Hydrogenation

Pt/MXene-enabled industrial flue gas waste heat-driven, dual-product selective photothermal catalytic reduction of CO2 with high efficiency

This study employs a photodeposition method to load Ag and Pt nanoparticles onto the surface and interlayered structure of MXene, developing an efficient catalyst for CO2 reduction in industrial flue gas. The catalyst exhibits excellent thermal catalytic performance within a low-temperature range of 60-100 °C, achieving CH4 and CO production rates of 461 μmol g-1 h-1 and 86 μmol g-1 h-1, respectively, with a CH4 selectivity of 84.3 %. This temperature range requires no additional heating, relying solely on residual heat from flue gas, which offers a distinct temperature advantage and high catalytic efficiency compared to most thermal and photothermal CO2 reduction processes. Under simulated sunlight and at 100 °C, the production rates for CH4 and CO are 34 μmol g-1 h-1 and 589 μmol g-1 h-1, respectively, with a CO selectivity of 94.5 %. Notably, the catalyst demonstrates dual-product selectivity under varying experimental conditions. Experimental characterization and density functional theory (DFT) calculations reveal the thermodynamic and kinetic mechanisms underlying the enhanced production rates and selectivity shifts in both thermal and photothermal catalysis, detailing the CO2 reduction pathways and Gibbs free energy changes across conditions. This study not only provides a new approach for low temperature CO2 catalytic reduction but also offers valuable insights into dual-product selectivity, demonstrating great potential for practical applications in industrial flue gas management.

Engineering Heteronuclear Dual-Metal Active Sites in Ordered Macroporous Architectures for Enhanced C2H4 Production from CO2 Photoreduction

Photocatalytic C2H4 synthesis from CO2 and H2O by utilizing solar energy represents a promising sustainable process, yet its efficiency remains significantly limited. Herein, we proposed a dual-engineered strategy integrating 3D ordered macroporous (3DOM) architectures with heteronuclear dual-metal active sites to synergistically promote the photocatalytic C2H4 production. As an example, the Cu/3DOM-In2O3 photocatalyst was synthesized by in situ incorporating Cu single atoms (Cu SAs) into 3DOM In2O3 through a template-assisted pyrolysis process. The strong interaction between Cu SAs and In2O3 resulted in the formation of charge-polarized Cu─In active sites along with abundant oxygen vacancies (OVs). 3DOM architectures serving as special nanoreactors displayed significant advantages in promoting CO2 enrichment and confining key intermediates, thereby increasing *CO coverage. Meanwhile, the charge-polarized Cu─In active sites effectively mitigated electrostatic repulsion and promoted the formation of *CO + *CHO intermediates, resulting in a thermodynamically spontaneous C─C coupling step. Therefore, the Cu/3DOM-In2O3 photocatalyst exhibited robust CO2 reduction to C2H4, achieving high C2H4 evolution rates under various CO2 concentrations, including pure CO2, 10% CO2 in Ar (simulated flue gas), and 0.04% CO2 in Ar (simulated air). This work offers a novel strategy for the construction of photocatalysts with tailored microstructures and specific active sites to promote the conversion of CO2 and H2O into multicarbon products.

Photocatalytic H2O2 Production with >30% Quantum Efficiency via Monovalent Copper Dynamics

Photocatalytic O2 reduction to H2O2 is a green and promising technology with advantages in cost-effectiveness, sustainability, and environmental friendliness, but its efficiency is constrained by limited selectivity for the two-electron oxygen reduction reaction (ORR) pathway. Here, we anchored isolated Cu atoms with tunable oxidation states onto WO3 as effective active centers to enhance photocatalytic H2O2 production. Due to the charge compensation between single atoms and the support, the oxidation state of Cu species exhibited a loading-dependent transition between +2 and +1 valence. Experimental and theoretical analyses indicate that Cu(I) sites exhibit outstanding O2 adsorption and activation capabilities, transforming the thermodynamically unfavorable hydrogenation of the *OOH intermediate (the rate-determining step in the two-electron ORR pathway) into an exothermic process, thereby significantly improving selectivity and efficiency. The Cu(I)-SA/WO3 photocatalyst exhibited a H2O2 production rate of 102 μmol h-1 under visible light irradiation, much higher than other reported photocatalysts. More importantly, it achieves an impressive apparent quantum efficiency of 30% at 420 nm, making a significant breakthrough in this field. This work provides novel perspectives for designing single-atom catalysts for efficient H2O2 synthesis via electronic state modulation.

Nitrogen Modified Linear Polythiophene Derivatives with Polarized Charge Distribution for Red Light-Induced Photocatalysis

Elevating the long-wavelength activation of photocatalysts represents a formidable approach to optimizing sunlight utilization. Polythiophene (PTh), although renowned for its robust light absorption and excellent conductivity, is largely overlooked for its potential as a photocatalyst due to the swift recombination of photogenerated charge carriers. Herein, we unveil that the strategic introduction of an aromatic ring containing varying nitrogen content into PTh instigates polarized charge distribution and facilitates the narrowing of the band gap, thereby achieving efficient photocatalytic activities for both hydrogen and hydrogen peroxide generation. Notably, the best sample, PTh-N2, even demonstrates photocatalytic activity in the red light region (600-700 nm). This study offers a promising avenue for the development of polymer photocatalysts with efficient photocatalytic performance for red light-induced photocatalysis.

Visible Light-Driven Acetaldehyde Production from CO2 and H2O via Synergistic Vacancies and Atomically Dispersed Cu Sites

Acetaldehyde (CH3CHO) is of great industrial importance and serves as a key intermediate in various organic transformations. Photocatalytic production of acetaldehyde from CO2 represents a sustainable route compared to conventional oxidation processes. However, current photocatalytic systems often face challenges, including limited product selectivity and dependence on sacrificial reagents. Here, we present a Cd0.6Zn0.4S (CZS) photocatalyst co-modified with sulfur vacancies and atomically dispersed Cu (Cu/CZS-Vs) for the efficient conversion of CO2 to acetaldehyde. Charge density analysis reveals that sulfur vacancies induce charge accumulation around the adjacent metal atoms, creating active sites that strongly anchor CO2 and H+, thereby promoting CO2 conversion while suppressing the competing hydrogen evolution reaction. The atomically dispersed Cu sites facilitate the conversion of key intermediates (i.e., *CHO and *CO) to the crucial C2 intermediate *OCCHO, which can subsequently be converted to acetaldehyde. As a result, this catalyst achieves an acetaldehyde yield of 121.5 μmol g-1 h-1 with a selectivity of ca. 80 % via photocatalytic CO2 conversion in the absence of sacrificial agents, along with a quantum efficiency of ca. 0.53 % at 400 nm, underscoring its potential for practical CO2 conversion applications. These results are expected to pave the way for future developments in green chemical processes.

Core-Shell MIL-125-NH2@FeOOH Nanocomposites for Highly Selective Photocatalytic Oxidation of Methane to Formaldehyde in Water Vapor

Formaldehyde (HCHO), a crucial industrial chemical, finds extensive applications across diverse sectors, including household products, commercial materials, aviation, and medical supplies. Methane (CH4), as an abundant C1 resource, presents a promising feedstock for HCHO synthesis. However, the direct conversion of CH4 to HCHO remains challenging due to its inherent chemical inertness, characterized by low polarizability and high C-H bond dissociation energy (439 kJ mol-1), coupled with the high reactivity of intermediate products. The development of efficient strategies for selective CH4 oxidation to high-value HCHO under mild conditions is therefore of significant practical importance. In this study, we developed a series of MIL-125-NH2@FeOOH-x heterostructured photocatalysts (FM-x) through the controlled deposition of FeOOH nanoparticles on MIL-125-NH2 surfaces. Comprehensive characterization and photocatalytic evaluations reveal that the optimized FM-1 catalyst facilitates in situ H2O2 generation and subsequent decomposition into hydroxyl radicals (•OH), enabling efficient CH4 photooxidation. Remarkably, the FM-1 catalyst achieves an exceptional HCHO production rate of 197.79 μmol·gcat-1 with >99.99% selectivity in water vapor, significantly outperforming both pristine FeOOH and MIL-125-NH2 components. This work presents a promising photocatalytic system for selective CH4 conversion, offering new insights into the design of efficient catalysts for C1 chemistry.

Probing local structure and electronic structure of α-Fe2O3/g-C3N4 S-scheme heterojunctions for boosting CO2 photoreduction

Construction of S-scheme heterojunction for photocatalytic conversion of CO2 into carbon-neutral fuels under sunlight is of paramount value for the sustainable development of energy. However, few reports are concerned the local structure and electronic structure of semiconductor heterojunction, which are importance of understanding the effect of heterojunction structure on the photocatalytic property. In this work, hierarchical α-Fe2O3/g-C3N4 S-scheme heterojunctions were manufactured via an in situ self-assembly strategy for the efficient reduction of CO2. The generation rate of main product CO for optimal α-Fe2O3/g-C3N4 heterojunction is up to 215.8 μmol g-1 h-1, with selectivity of 93.3 %, which is 17.5 and 6.1 times higher than those of pristine Fe2O3 and g-C3N4, respectively. The local structure and electronic structure for α-Fe2O3/g-C3N4 heterojunction are probed by hard X-Ray Absorption Fine Structure (XAFS) and soft X-Ray Absorption Spectroscopy (XAS), as well as density-functional theory (DFT) calculations. It is found that the Fe(d)-N(p) bond formed in α-Fe2O3/g-C3N4 heterojunction precisely connects the conduction band (CB) of Fe2O3 and the valence band (VB) of g-C3N4, which minimizes the charge transfer distance and facilitates CO2 photoreduction activity. This work provides important information for understanding the influence of interface local and electronic structure on the performance of photo-catalytic reduction of CO2 at the atomic level.

Synergistic Ru Species on Poly(heptazine imide) Enabling Efficient Photocatalytic CO2 Reduction with H2O beyond 800 nm

Photocatalytic CO2 conversion with H2O to carbonaceous fuels is a desirable strategy for CO2 management and solar utilization, yet its efficiency remains suboptimal. Herein, efficient and durable CO2 photoreduction is realized over a RuNPs/Ru-PHI catalyst assembled by anchoring Ru single atoms (SAs) and nanoparticles (NPs) onto poly(heptazine imide) (PHI) via the in-plane Ru-N4 coordination and interfacial Ru-N bonds, respectively. This catalyst shows an unsurpassed CO production (32.8 µmol h-1), a record-high apparent quantum efficiency (0.26%) beyond 800 nm, and the formation of the valuable H2O2. Ru SAs tune PHI's electronic structure to promote in-plane charge transfer to Ru NPs, forming a built-in electron field at the interface, which directs electron-hole separation and rushes excited electron movement from Ru-PHI to Ru NPs. Simultaneously, Ru SAs introduce an impurity level in PHI to endow long-wavelength photoabsorption, while Ru NPs strengthen CO2 adsorption/activation and expedite CO desorption. These effects of Ru species together effectively ensure CO2-to-CO conversion. The CO2 reduction on the catalyst is revealed to follow the pathway CO2→ *CO2→ *COOH→ *CO→ CO, based on the intermediates identified by in situ diffuse reflectance infrared Fourier transform spectroscopy and further supported by density functional theory calculations.

Single-Atom Fe Catalysts With Improved Metal Loading for Efficient Ammonia Synthesis Under Mild Conditions

Ammonia synthesis is a cornerstone in the chemical industry. Given that the traditional Haber-Bosch (H-B) process requires very high temperature and pressure, it is imperative to develop catalysts capable of facilitating ammonia synthesis under mild conditions. In this work, a post-metal replacement strategy is developed to improve the Fe loading in single-atom Fe-implanted N-doped carbon catalysts. Starting from the Zn-Fe-N-C material with single-atom Zn and Fe sites coexisting in N-doped porous carbon pyrolyzed from porphyrinic metal-organic frameworks (MOFs), the replacement of single-atom Zn with Fe sites is performed, which significantly increases the Fe loading from 1.33 to 2.39 wt%. This effectively suppresses the migration and agglomeration of Fe, yielding Fe-N-C with high metal loading (FeHL-N-C). Notably, the FeHL-N-C catalyst exhibits a catalytic rate of 558 µmol·gcat -1·h-1 at 300 °C for ammonia synthesis at atmospheric pressure, far surpassing the performance of the traditional dominant fused iron and even Ru-based precious metal catalysts.

Exceptional CO2 Hydrogenation to Ethanol via Precise Single-Atom Ir Deposition on Functional P Islands

The thermocatalytic hydrogenation of CO2 to ethanol has attracted significant interest because ethanol offers ease of transport and substantial value in chemical synthesis. Here, we present a state-of-the-art catalyst for the CO2 hydrogenation to ethanol achieved by precisely depositing single-atom Ir species on P cluster islands situated on the In2O3 nanosheets. The Ir1-Px/In2O3 catalyst achieves an impressive ethanol yield of 3.33 mmol g-1 h-1 and a turnover frequency (TOF) of 914 h-1 under 1.0 MPa (H2/CO2=3 : 1) at 180 °C, nearly 8 times higher than that of the unmodified Ir1/In2O3 catalyst. Additionally, at a more industrially relevant pressure of 5.0 MPa, the TOF of the Ir1-Px/In2O3 catalyst can reach up to 2108 h-1, surpassing previously reported catalysts. Combined in situ characterization and theoretical studies reveal that the hydrogenation process is significantly enhanced by the Ir1-Px entities. Specifically, the Ir atom facilitates CO2 activation and C-C coupling, while the surrounding P island exhibits exceptional H2 dissociation ability. These three steps have been found crucial for the CO2 hydrogenation reaction. This discovery opens new opportunities for the regulation of the microenvironment of current catalysts by providing essential chemical functionalities that enhance intricate and complex reaction processes.

Tailoring Oxygen Vacancies with Atomically Dispersed Cu Sites for Stable and Efficient Photothermal CO2 Conversion

Photothermal catalysis under mild conditions represents a promising and sustainable approach for CO2 conversion into high-value chemicals, thereby enabling efficient carbon recycling. However, precise manipulation of active sites and their coordination environments at the atomic level to enhance catalyst performance still remains a challenge. Here, we present a single-atom doping strategy for oxygen vacancy engineering to facilitate efficient CO2 conversion. Specifically, an In2O3-based catalyst with abundant oxygen vacancies induced by homogeneously dispersed Cu single atoms is constructed, exhibiting a competent CO2 reduction performance in photothermal reverse water-gas shift reaction. The optimal Cu-In2O3 catalyst achieves a CO yield rate of 46.17 mol gCu -1 h-1 with near-unity selectivity (>99%) and demonstrates stability over 450 h under 3 W cm-2 full-spectrum light illumination. Comprehensive spectroscopic characterization and computational simulations elucidate that the Cu single atoms synergistically interact with oxygen vacancies to promote H2 dissociation and CO2 activation under photoexcitation. This work provides insights into the design of photothermal catalysts, emphasizing the transformative potential of atomic-site engineering for efficient CO2 conversion and sustainable energy technologies.

Designed synthesis of multi-defective Ti0.9Cu0.1N@Pt as a robust catalyst for the oxygen reduction reaction

Proton-exchange membrane (PEM) fuel cells require cost-effective and robust catalysts capable of withstanding high levels of operation. However, the sluggish cathode oxygen reduction reaction (ORR) and the high cost and instability of the currently used catalysts present significant challenges for the commercialization of PEMFCs. To address these issues, multi-defective Cu-titanium nitride (Ti0.9Cu0.1N) nanospheres with a large surface area are synthesized, and then deposited with a thin layer of Pt, forming a Ti0.9Cu0.1N@Pt catalyst. Compared to commercial Pt/C catalysts, this Ti0.9Cu0.1N@Pt catalyst demonstrates a 53 mV greater half-wave potential in acidic media, indicating its improved ORR performance. Additionally, the Ti0.9Cu0.1N@Pt catalyst can maintain a high mass activity retention of 63% after 6000 accelerating cycle tests, whereas commercial Pt/C catalysts lose 70% of their mass activity. These findings indicate the promising potential for developing and implementing a binary nitride support to enhance Pt utilization in the near future.

Pt single atoms promoting the construction of asymmetric double sites to achieve highly selective photoreduction of CO2 to ethylene

In this work, Pt single atoms (SAs) were engineered on the surface of CdIn2S4 (CIS) to trigger abundant generation and stable existence of sulfur vacancies (Sv). Through quasi in situ X-ray photoelectron spectroscopy (XPS) and work function analysis, the photogenerated electrons are first captured by Pt SAs and Sv, and then transferred from Pt SAs to Sv, ultimately increasing the electron density of Sv. Meanwhile, Sv have significant advantages in adsorbing CO2 molecules. According to the number of transferred electrons, the optimized 0.8 %Pt/CIS has 76 times the photocatalytic performance of pristine CIS, and the selectivity of ethylene (C2H4) is up to 99.3 %. The carbon-carbon coupling reaction between *CO and *CHO adsorbed on double sites of Sv and In atoms is identified as the rate-determining step. Theoretical calculations suggest that the energy barrier required for coupling of intermediates *CO and *CHO is the lowest, conducive to the selective generation of C2H4.

Photothermal Catalytic Recycling of Polyester Over Magnetic Ni-MnOx Nanocatalyst

The solar-driven catalytic recycling of plastics has recently emerged as a new frontier in industry. Nevertheless, its large-scale application requires the catalysts being capable of the strong absorption of visible and near-infrared light, strengthened photothermal efficiency, high activity and selective toward target product, enhanced stability, as well as easy separation from the products. In this work, magnetic Ni-MnOx nanocatalyst (MN/C) is synthesized via the pyrolysis of metal-organic framework (MOF) for the photothermal catalytic recycling of polyethylene terephthalate (PET) to bis(2-hydroxyethyl) terephthalate (BHET). Detailed investigations demonstrate that the strong interaction between MnOx and Ni enables H2 spill-over from Ni to Mn species and electron transfer from Mn to Ni, where MnOx plays the active sites and Ni promotes the efficiency for photo-to-heat conversion, as a result of significantly enhanced photothermal catalytic performance. Consequently, PET is completely converted after photothermal recycling for 30 min (0.84 W cm-2) at 190 °C, with a BHET selectivity of ≈79%. Moreover, MN/C has been successfully applied for recycling PET from various sources. In addition to the promising performance, the low-cost and easy magnetic separation of MN/C will further contribute to the sustainable recycling of plastics.

Merger of Single-Atom Catalysis and Photothermal Catalysis for Future Chemical Production

Photothermal catalysis is an emerging field with significant potential for sustainable chemical production processes. The merger of single-atom catalysts (SACs) and photothermal catalysis has garnered widespread attention for its ability to achieve precise bond activation and superior catalytic performance. This review provides a comprehensive overview of the recent progress of SACs in photothermal catalysis, focusing on their underlying mechanisms and applications. The dynamic structural evolution of SACs during photothermal processes is highlighted, and the current advancements and future perspectives in the design, screening, and scaling up of SACs for photothermal processes are discussed. This review aims to provide insights into their continued development in this rapidly evolving field.

Isolated Ni Atoms for Enhanced Photocatalytic H2O2 Performance with 1.05% Solar-to-Chemical Conversion Efficiency in Pure Water

Photocatalytic hydrogen peroxide (H2O2) production encounters a major impediment in its low solar-to-chemical conversion (SCC) efficiency due to undesired H2O2 product decomposition. Herein, an isolated nickel (Ni) atom modification strategy is developed to adjust the thermodynamic process of H2O2 production to address the challenge. Sacrificial experiments and in situ characterization reveal that H2O2 generation occurs via a highly selective indirect two-electron oxygen reduction reaction. The optimized photocatalyst exhibits a remarkable H2O2 production rate of 338.9 μmol gcat-1 h-1 in pure water, representing a 48-fold enhancement. Notably, it attains an impressive SCC efficiency of 1.05%, surpassing that of current state-of-the-art catalysts. Theoretical insights reveal the downshifted d-band center facilitates moderate O2 adsorption and barrier-free *OOH conversion, favoring H2O2 release and preventing *H2O2 decomposition. This work showcases efficient H2O2 photosynthesis via d-band manipulation, presenting a fresh perspective for advancing high-efficiency SCC systems.