Hydroxyaldehydes are terminally differentiated building blocks and key intermediates for organic synthesis. Unsymmetric oxidation of α,ω-diols to aliphatic hydroxyaldehydes is rarely developed due to the tremendous difficulties and challenges to avoid overoxidation. Here, we disclose a heterogeneous photocatalytic approach with Pt-loaded TiO2 as a photocatalyst to realize the semioxidation of α,ω-diols to aliphatic hydroxyaldehydes. 6-Hydroxyhexanal is produced via photocatalytic dehydrogenation of 1,6-hexanediol at a rate of ca. 21.7 g/m2/h with selectivity higher than 96% and simultaneous generation of stoichiometric amounts of H2. The absence of aggressive oxygen-based radical species, appropriately controlled oxidation capacity of photogenerated holes, low affinity of hydroxyaldehyde for photocatalysts in the suitable acetonitrile solvent matrix, and fine-tuned reaction temperature ensure that the oxidation of 1,6-hexanediol terminates at 6-hydroxyhexanal. This work reports on a conceptual breakthrough in photocatalytic interface design for high-value-added molecular synthesis via controlled surface redox reactions.

Thermal oxidation of bulky carbon nitride (C3N4, CN) to expose more active sites is an important method to improve the activity of the as-prepared CN nanosheets. Unfortunately, the yield of thermal oxidation is low. Herein, we report dual-deficient CN (DDCN) ultrathin nanosheets engineered with nitrogen vacancies and cyano groups by two-step bottom-up thermal polymerization of belt-like melamine with a high yield of 65 %. Featured with abundant exposed active sites, short charge migration distance, wide visible-light absorption, quick charge separation/transfer, enhanced oxygen adsorption ability and 2e oxygen reduction reaction selectivity, the DDCN exhibits a high H2O2 production rate of similar to 1031 mu mol g(1) h(1), which is 19.5 times that of CN (53 mu mol g(1) h(1)) under visible light irradiation (lambda >= 420 nm). Specifically, the apparent quantum yield (AQY) of DDCN reached 10.7 % at 420 nm. This study provides a facile dual-defect engineering method to develop highly efficient ultrathin CN-based photocatalysts.

Photoreduction of CO2 and H2O into fuels and value-added chemicals is an effective solution to address global energy issues. However, developing photocatalysts with high activity and selectivity remains a major challenge. Herein, we report Ag nanoparticles (NPs) loaded FeVO4 (FVO) composite photocatalyst for highly efficient and selective photoreduction of CO2 to CO. Under a 300 W Xe lamp irradiation, the optimal Ag-1-FVO catalyst exhibits a CO yield of 255.4 mu mol g(-1) h(-1) and a CO selectivity of 99.7 %, which are dramatically higher than those of pure FVO alone. The significantly enhanced photocatalytic performance could be attributed to Ag NPs on the surface of FVO, which improve the separation efficiency of photogenerated carriers and promote the adsorption/activation of CO2 molecules. This study suggests that modification of semiconductor photocatalysts with Ag NPs is an effective method for enhancing the CO2 photoreduction activity.

The increased light absorption, reactive sites, CO 2 adsorption/activation, and desorption energy barrier of CO* in Co/TiO 2 –TiN synergistically account for the selective photothermocatalytic CO 2 reduction into CH 4 .

Photocatalytic oxidation of methane to liquid oxygenates offers a sustainable strategy for utilizing natural gas and reducing carbon emissions. However, the efficiency of current photocatalysts remains limited by poor charge carrier utilization, particularly the ineffective migration of holes that are crucial for C─H bond activation. Herein, we report a rationally engineered TiO 2 photocatalyst incorporating atomically dispersed Pd and a gradient distribution of Ti 3+ species, achieving a remarkable C 1 oxygenates yield of 8.14 mmol·g cat −1 ·h −1 with 91.3% selectivity at room temperature, surpassing most state‐of‐the‐art photocatalysts. Comprehensive characterizations and theoretical calculations reveal that Pd single atoms accelerate electron transfer and facilitate O 2 dissociation, while the gradient‐distributed Ti 3+ species promote hole migration from the bulk to the surface, enabling efficient CH 4 activation. These spatially separated charge pathways synergistically promote the formation of • CH 3 and • OOH radicals, which couple to generate CH 3 OOH and subsequently convert into methanol and formaldehyde.

Methylamine hydrochlorides (MACls) are important building blocks in organic synthesis, yet their conventional production requires energy-intensive, multistep processes. Herein, we report a photocatalytic strategy for the direct synthesis of MACls from methanol and ammonium chloride under mild conditions. A high MACls yield of 29.62 mmol·g-1 is achieved within 4 h over Pd-decorated TiO2 with oxygen vacancies, outperforming most previously reported photocatalytic C-N coupling systems. In situ spectroscopy, isotope effects, and theoretical studies reveal that methanol is initially oxidized to formaldehyde, a key intermediate that reacts with ammonium chloride via nucleophilic condensation and successive methylation to form C-N bonds, thereby yielding MACls. Photoexcitation enables both the thermodynamically and kinetically unfavorable methanol-to-formaldehyde conversion and drives stepwise methylation reactions, which are otherwise inactive in the dark. The cooperative interaction between Pd and oxygen vacancies promotes charge separation and methanol dehydrogenation, resulting in highly efficient MACls photosynthesis. This work advances mechanistic insights into photocatalytic C-N bond formation and presents a sustainable approach for producing value-added C-N compounds from simple C1 and nitrogen feedstocks.

Visible-light-driven photocatalytic hydrogen production is one of the ideal green technologies for solar-to-chemical energy conversion. Carbon nitride (C3N4, CN) has been attracting extensive attention for its suitable band structure and stability, but the efficiency of photocatalytic hydrogen evolution is low due to insufficient visible-light absorption and rapid charge recombination. Herein, we develop a novel (F, K)-co-doped CN (FKCN) catalyst via a facile thermal polymerization approach using KOH-modified melamine and NH4F as the dopant precursors. The FKCN catalyst demonstrates broadened light absorption, significantly enhanced charge separation, and excellent cyclic stability. And the optimal F(0.15)K(6)CN catalyst achieves a hydrogen evolution rate of as high as 3101.5 μmol g−1 h−1 (12-fold that of pristine CN) under visible-light irradiation (λ ≥ 420 nm), which is among the best element-doped CN photocatalysts. This work highlights the effectiveness of a multi-element doping strategy in designing CN-based photocatalysts for efficient hydrogen evolution.

Constructing a heterojunction is considered one of the most effective strategies for enhancing photocatalytic activity. Herein, we employ Ta3N5 and tubular graphitic carbon nitride (TCN) to construct a Ta3N5/TCN van der Waals heterojunction via electrostatic self-assembly for enhanced photocatalytic H2 production. SEM and TEM results show that Ta3N5 particles (~300 nm in size) are successfully anchored onto the surface of TCN. The light absorption capability of the Ta3N5/TCN heterojunction is between those of Ta3N5 and TCN. The strong interaction between Ta3N5 and TCN with different energy structures (Fermi levels) by van der Waals force renders the formation of an interfacial electric field to drive the separation and transfer of photogenerated charge carriers in the Ta3N5/TCN heterojunction, as evidenced by the photoluminescence (PL) and photoelectrochemical (PEC) characterization results. Consequently, the optimal Ta3N5/TCN heterojunction exhibits a remarkable H2 production rate of 12.73 mmol g−1 h−1 under visible light irradiation, which is 3.3 and 16.8 times those of TCN and Ta3N5, respectively. Meanwhile, the cyclic experiment demonstrates excellent stability of the Ta3N5/TCN heterojunction upon photocatalytic reaction. Notably, the photocatalytic performance of 15-TaN/TCN outperforms the most previously reported CN-based and Ta3N5-based heterojunctions for H2 production. This work provides a new avenue for the rational design of CN-based van der Waals heterojunction photocatalysts with enhanced photocatalytic activity.

The efficiency of CO2 photoreduction is often limited by the low reactivity of CO2 molecules and the rapid recombination of photogenerated charge carriers in most of the photocatalysts developed so far. In this study, we report a newly developed p-type Bi2Te3/SrTiO3 (pBT/STO) nanocomposite for efficient CO2 photoreduction. Upon light irradiation, the thermoelectric pBT with a strong light absorption capacity generates the photothermal effect favoring the activation of CO2 molecules. Meanwhile, a temperature gradient formed in pBT induces a thermoelectric field via the Seebeck effect, which promotes the charge carriers’ separation/transfer. In addition, the excellent electric conductivity and large work function render pBT an efficient cocatalyst for further improving the charge carriers’ separation/transfer. Owing to the synergistic photothermoelectric (PTE) effect on activation of CO2 molecules and promotion of charge separation/transfer, the efficiency of CO2 photoreduction over pBT/STO is significantly enhanced. We achieve the highest CO evolution rate of 28.0 μmol·gcat−1·h−1 over the optimal pBT(3)/STO, which is 12.8 times that of pure STO. This work suggests that a thermoelectric material and a semiconductor can be incorporated into a nanocomposite system for efficient CO2 reduction via the synergistic photothermoelectric effect on activating the CO2 molecules and promoting the charge carriers’ separation/transfer.

The direct photocatalytic oxidation of methane to value-added chemicals has garnered considerable interest in recent years. However, achieving high productivity while maintaining high selectivity at an appreciable methane conversion rate remains a formidable challenge. Here, we present photochemically-triggered and photothermally-enhanced oxidative coupling of methane to multi-carbon C2+ alkanes over an Au and CeO2 nanoparticle-decorated ZnO photocatalyst, which exhibits a record-breaking C2+ production rate of 17,260 μmol g−1 h−1 with ~90% C2+ selectivity under wide-spectrum light irradiation without a secondary source of heating. Comprehensive characterizations and computational studies reveal that CH4 activation is a photochemical reaction initiated by ultraviolet light-excited ZnO, and the introduction of CeO2 substantially enhances the activation of CH4 and O2 due to the cooperative interaction between Au and CeO2. Concurrently, Au nanoparticles capture visible and near-infrared light to generate localized heating, which greatly promotes the subsequent desorption of produced methyl radical for C–C coupling prior to undergoing further undesired overoxidation. Achieving both high activity and selectivity in CH4 photooxidation to C2+ hydrocarbons is challenging. This work shows that integrating photochemical and photothermal effects enhances both, enabling efficient CH4 oxidative coupling to C2+ alkanes.

Photocatalytic oxidation of methane to liquid oxygenates offers a sustainable strategy for utilizing natural gas and reducing carbon emissions. However, the efficiency of current photocatalysts remains limited by poor charge carrier utilization, particularly the ineffective migration of holes that are crucial for C─H bond activation. Herein, we report a rationally engineered TiO 2 photocatalyst incorporating atomically dispersed Pd and a gradient distribution of Ti 3+ species, achieving a remarkable C 1 oxygenates yield of 8.14 mmol·g cat −1 ·h −1 with 91.3% selectivity at room temperature, surpassing most state-of-the-art photocatalysts. Comprehensive characterizations and theoretical calculations reveal that Pd single atoms accelerate electron transfer and facilitate O 2 dissociation, while the gradient-distributed Ti 3+ species promote hole migration from the bulk to the surface, enabling efficient CH 4 activation. These spatially separated charge pathways synergistically promote the formation of • CH 3 and • OOH radicals, which couple to generate CH 3 OOH and subsequently convert into methanol and formaldehyde.

Photoreduction of CO2 and H2O into fuels and value-added chemicals is a promising green technology for solar-to-chemical conversion. However, improving the conversion efficiency with regulated product selectivity is a big challenge due to the sluggish dynamic transfer and insufficient active sites. Herein, we report on Pt single atoms anchored porous C3N4 nanosheet photocatalyst (Pt1@CN) with Pt–N4 coordination for stable and efficient CO2 photoreduction using H2O as reductant. The Pt1@CN exhibits an evolution rate of 84.8 μmol g−1 h−1 with nearly 100% CO selectivity, outperforming most previous C3N4-based single-atom photocatalysts. Experimental and DFT calculation results reveal that the Pt–N4 coordinated active sites promote the photogenerated electron transfer, CO2 adsorption/activation, *COOH generation, and *CO desorption, thus accounting for the significantly improved CO2 photoreduction activity with ∼100% CO selectivity. This study provides a deep insight into the significant roles of single-atom active sites in enhancing the CO2 photoreduction activity and regulating the product selectivity.

As a promising technology to mitigate global carbon emissions, photothermal catalytic CO 2 reduction remains a great challenge in increasing the conversion efficiency and regulating the product selectivity. Herein, a series of phase‐separated Ni–Mo alloy catalysts for efficient photothermal CO 2 reduction with tunable CO selectivity is reported. With the increase of Mo content, the evolution rate and selectivity of CO increases. The optimal catalyst Ni 1 Mo 1 achieves 32.1% CO 2 conversion with 98.0% of CO selectivity and 71.1 mmol g cat −1 h −1 of CO evolution rate under a 300 W xenon lamp irradiation. Further increasing the Mo content reduces the CO evolution rate while maintaining the high CO selectivity. In the mechanistic study, it is revealed that the Ni–Mo alloy with an appropriate Ni/Mo ratio (e.g., Ni 1 Mo 1 ) possesses a modified electronic structure with more negative d‐band center, which increases the light absorption, reduces the H 2 dissociation, and favors the CO desorption, thereby leading to efficient and selective photothermal reduction of CO 2 to CO. In this work, a viable strategy to design nickel‐based catalysts is provided for efficient and selective photothermal CO 2 reduction via composition‐mediated modification of electronic structure.

Photoreduction of CO2 into value-added chemicals and fuels is a promising green technology for solar-to-chemical conversion. Owing to the atomic utilization, unique metal-support interaction, and unsaturated coordination active sites, single-atom catalysts (SACs) have been attracting great attention in achieving high activity and selectivity of CO2 photoreduction reactions. On the other hand, carbon nitride (C3N4) with abundant periodically unsaturated coordination of nitrogen atoms can serve as an excellent support for anchoring metal single atoms. In this context, extensive research efforts have been paid in C3N4-based SACs for CO2 photoreduction in recent years. In this review, we report the recent advances in C3N4 supported SACs for CO2 photoreduction. We start from the introduction of synthetic strategies of various C3N4 supported metal SACs. Secondly, the main advanced characterization techniques and calculation methods for identifying the single-atoms and their coordination environments of C3N4-based SACs are summarized. Thirdly, some state-of-the-art works on the rational design of C3N4-based SACs and their applications in CO2 photoreduction are introduced. Lastly, we briefly summarize the main challenges and propose important perspectives of C3N4-based SACs in CO2 photoreduction. This review is expected to provide some useful guidelines for the development of efficient and stable C3N4-based SACs for CO2 photoreduction.

Photothermal catalytic carbon dioxide (CO2) reduction has attracted increasing research attention as a promising method for recycling CO2 and producing renewable energy. However, it remains a challenge in the improvement of catalytic activity with regulated product selectivity in view of practical applications. Herein, we develop the two-dimensional layered V2C MXene (VC) supported Ni nanoparticle and NiO nanosheet (Ni@NiO/VC) composite as an efficient catalyst for selective photothermal reduction of CO2 to CH4. The optimal 0.8Ni@NiO/VC catalyst exhibits 48.1% of CO2 conversion with an evolution rate of 33.2 mmol·gcat−1·h−1 and 99.2% selectivity for CH4 production under a 300 W full-arc xenon lamp irradiation. Moreover, a long term of cyclic photothermal CO2 reduction reaction demonstrates the excellent stability of 0.8Ni@NiO/VC. The enhanced photothermal CO2 reduction activity with a high CH4 selectivity could be attributed to the large specific surface area and excellent photothermal effect of V2C MXene, and the synergistic effect of Ni and NiO on adsorption/activation of H2 and CO2 molecules. This work provides a feasible strategy for the construction of efficient photothermal CO2 reduction catalyst by properly incorporating transition metal nanoparticles and metal oxide with a suitable MXene.

Artificial photosynthesis utilizing solar energy to convert carbon dioxide (CO2) and water (H2O) into fuels and high-value chemicals offers a promising technology for mitigating energy consumption and environmental pollution. However, the development of efficient photocatalysts with high product selectivity remains a big challenge due to the sluggish dynamic transfer of photogenerated charge carriers. Herein, porous C3N4 nanosheet supported Au single atoms photocatalyst (Au1@CN) with Au-N4 coordination is fabricated via a facile "impregnation + freeze-drying" process. The as-synthesized Au1@CN exhibits efficient and stable CO2 photoreduction activity with a CO evolution rate of 0.58 mu mol h-1 (amount of catalyst: 10 mg), CO selectivity of 94 %, and a turnover frequency (TOF) of 10.0 h-1 using H2O as the reductant, which exceed most previous works on C3N4-based single-atom photocatalysts for CO2 reduction. Experimental studies and density functional theory (DFT) calculations reveal that the unique Au-N4 coordination promotes the dynamic transfer of photogenerated charge carriers, facilitates the adsorption/activation of CO2 molecules and generation of *COOH intermediate, thereby significantly enhancing the CO2 photoreduction activity with high CO selectivity. This study demonstrates an effective strategy for the design of M-N4 coordinated single-atom catalyst toward efficient and selective photoreduction of CO2 to CO.

Direct photocatalytic methane oxidation to produce liquid oxygenates offers a promising approach for the upgrading of abundant methane under mild conditions, yet it remains a formidable challenge in achieving high reaction rates while maintaining high selectivity. Herein, we report the highly dispersed CuOx and Pd nanodots decorated TiO2 for photocatalytic oxidation of CH4 with O2 at room temperature, which exhibits a remarkable C1 oxygenates production rate of 39.5 mmol center dot g- 1 center dot h- 1 with a nearly 100 % selectivity, outperforming most of the state-of-the-art photocatalysts. Both experimental and theoretical studies suggest that the impressive photocatalytic performance is attributed to the synergy of Cu+ species and Pd nanodots. Cu+ species not only promote the interfacial electrons transfer from TiO2 to Pd, but also mediate CH4 oxidation reaction to avoid overoxidation of oxygenates to CO2, while the resulting electron-rich Pd sites boost the production of primary products (CH3OOH and CH3OH) by lowering the reaction energy. This work provides a new pathway for developing highly efficient photocatalysts for the selective conversion of methane to value-added chemicals by designing bimetallic cocatalysts.

Photocatalytic overall water splitting is an ideal green technology to produce the clean and renewable hydrogen energy. Herein, high crystalline zigzag GaN nanowires (NWs) are successfully synthesized through an Au -catalyzed chemical vapor deposition process. The single-crystalline zigzag nanowire is a polar-surface -dominated nanostructure composed of Ga and N atoms alternately as a result of the inherent surface atomic termination and polar charges. Compared with the non-polar-dominated smooth-surfaced nanowires, the zigzag nanowires attain multifold H2 and O2 evolutions in the presence of respective sacrificial reagents. More importantly, the zigzag nanowires realize the stoichiometric overall pure water splitting, due to the synergistic effect of the internal electric field between Ga-terminated and N-terminated facets that drives the spatial charge separation, the high charge mobility and polar surface energy. This work suggests that constructing polar surface on one-dimensional nanomaterial with spatially separated H2 and O2 evolution sites could be employed as a new crystal engineering strategy for designing efficient photocatalysts towards overall water splitting.

Li-rich materials have become one of the most promising cathode candidates for next-generation lithium-ion battery systems due to their high capacity and operating voltage. Conventional O3-type Li-rich materials undergo a structural transition from a layered to a spinel phase during cycling, leading to the degradation in their electrochemical performance, especially in terms of their voltage decay. The oxygen atoms comprising the structure of O2-type Li-rich materials are stacked in the ABAC configuration, which can effectively suppress these harmful phase transitions. However, O2-type Li-rich materials are metastable structures and can only be synthesized via the means of complex ion exchange methods. In addition, the surface of the material is susceptible to side reactions with the electrolyte when charged to high voltages. Here, we explored the optimal conditions for the synthesis of O2-type Li[Li0.25Ni0.1Co0.05Mn0.6]O2 (LLNCM) in more detail by preparing the precursors using the sol-gel method. Meanwhile, the modification of the material’s surface via low-temperature hydrolysis of aluminum isopropoxide has been proposed for the first time in this study to avoid the damage of metastable materials by the high-temperature coating process. The surface-modified materials prepared under optimal conditions exhibited an excellent electrochemical performance, indicating that a highly stable O2-type bulk phase structure with effective surface modification is a potential way to promote the commercial applications of Li-rich cathode materials.

Cocatalyst plays a critical role in photocatalytic overall water splitting (POWS). However, the typical metal cocatalysts aimed at promoting hydrogen evolution are also highly active for H2-O2 recombination. Here we report a new strategic approach of coating single-layer graphene selectively on metal cocatalyst by chemical vapor deposition to effectively suppress the backward reaction for efficient POWS. Pt@C/SrTiO3 demonstrates steady POWS activity in contrast to the rapid activity decline by 65% in 5 h of Pt/SrTiO3, and no obvious H2 and O2 consumption is observed over Pt@C/SrTiO3 during dark reaction. Experimental and theoretical calculation results indicate that the graphene prevents O2 from contacting Pt and the O2 dissociation as the rate-determining step of backward reaction is retarded. Moreover, this method demonstrates good universality and similar suppressing effect is also achieved over Rh, Pd@C. These findings may open a new pathway for developing effective cocatalysts with suppressed backward reaction for efficient POWS.