The oxygen atom coordination inducing the structure reconstruction of the catalytic site is identified and recognized ambiguously, which is related to accurately declare the mechanism in a dynamic catalytic process. Herein, we demonstrated that the reconstructed catalytic sites would lead to a remarkable performance for photocatalytic CO₂ reduction. At the initial 4-cycles testing, the in-situ formation of CoO_x active sites on the Co (CoP) surface performed an increasing transient activity and selectivity toward CO evolution. The formation of reconstructive Co-O bond and the appearance of intermediate specie CO were simultaneously observed by the pre-operando Raman, revealing the dynamic relationship between catalytic site structure and the photocatalytic properties. Moreover, density functional theory calculations showed that the electronic structure of the reconstructive surface sites could modulate the ability of CO₂ adsorption and CO desorption. The reduced barrier energy for the rate-determining step finally improved the activity and selectivity of CO₂ reduction.

Photosensitized heterogeneous CO₂ reduction (PHCR) has emerged as a promising means to convert CO₂ into valuable chemicals, however, challenged by the relatively low carbonaceous product selectivity caused by the competing hydrogen evolution reaction (HER). Here, we report a PHCR system that couples Ru(bpy)₃²⁺ photosensitizer with {001} faceted LiCoO₂ nanosheets photocatalyst to simultaneously yield 21.2 and 722 μmol·g⁻¹·h⁻¹ of CO, and 4.42 and 108 μmol·g⁻¹·h⁻¹ of CH₄ under the visible light and the simulated sunlight irradiations, respectively, with completely suppressed HER. The experimental and theoretical studies reveal that the favored CO₂ adsorption on the exposed Li sites on {001} faceted LiCoO₂ surface is responsible for the completely suppressed HER.

To data, using strong metal-support interaction (SMSI) effect to improve the catalytic performance of metal catalysts is an important strategy for heterogeneous catalysis, and this effect is basically achieved by using reducible metal oxides. However, the formation of SMSI between metal and inert-support has been so little coverage and remains challenge. In this work, the SMSI effect can be effectively extended to the inert support-metal catalysis system to fabricate a Cu⁰/Cu-doped SiO₂ catalyst with high dispersion and loading (38.5 wt.%) through the interfacial effect of inert silica. In the catalyst, subnanometric composite of Cu cluster and atomic copper (in the configuration of Cu–O–Si) can be consciously formed on the silica interface, and verified by extended X-ray absorption fine structure (EXAFS), in situ X-ray photoelectron spectroscopy (XPS), and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) characterization. The promoting activity in transfer-hydrogenation by the SMSI effect of Cu-silica interface and the synergistic active roles of cluster and atomic Cu have also been revealed from surface interface structure, catalytic activity, and density functional theory (DFT) theoretical calculation at an atomic level. The subnanometric composite of cluster and atomic copper species can be derived from a facile synthesis strategy of metal-inert support SMSI effect and the realistic active site of Cu-based catalyst can also been identified accurately, thus it will help to expand the application of subnanometric materials in industrial catalysis.

The cyclopentanone and derivatives are a class of crucial fine chemicals for various industries and currently produced by conventional petrochemical synthetic routes. Here, we demonstrated a new synthetic approach to directly fabricate N-doped carbon nanotube (N-CNTs) networks with confined Co nanoparticles from Co²⁺-impregnated bulk g-C₃N₄ as high performance hydrogenation rearrangement (HR) catalyst to efficiently convert a wide spectrum of biomass-derived furanic aldehydes to the corresponding cyclopentanones in water under a record-low H₂ pressure of 0.5 MPa and mild temperature. We unveiled a Co-catalysed bulk g-C₃N₄ decomposition/carbonisation CNTs formation mechanism. A new HR pathway was also unveiled.

Electrochemical water splitting is quite seductive for eco-friendly hydrogen fuel energy production, however, the attainment of highly efficient, durable, and cheap catalysts for the hydrogen evolution reaction (HER) remains challenging. In this study, molybdenum oxides stabilized palladium nanoparticle catalysts (MoO_x-Pd) are in situ prepared on commercial carbon cloth (CC) by the facile two-step method of dip-coating and electrochemical reduction. As a self-supported Pd-based catalyst electrode, the MoO_x-Pd/CC presents a competitive Tafel slope of 45.75 mV·dec^-1, an ultralow overpotential of 25 mV, and extremely long cycling durability (one week) in 0.5 M H₂SO₄ electrolyte, superior to unmodified Pd catalysts and comparable to commercial Pt mesh electrode. On the one hand, the introduction of MoO_x can inhibit the growth of Pd particles to obtain ultrafine Pd nanoparticles, thus exposing more available active sites. On the other hand, density functional theory (DFT) calculation revealed that MoO_x on the surface of Pd metal can regulate the electronic structure of Pd metal and enhance its intrinsic catalytic activity of HER. This work suggests that transitional metal nanoparticles stabilized by molybdenum oxides are hopeful approaches for obtaining fruitful hydrogen-producing electrocatalysts.

The development of a facile method to construct a high-performance electrode is of paramount importance to the application of alkaline water electrolysis. Here, we report that the activity of nickel foam (NF) towards the oxygen evolution reaction (OER) can be enhanced remarkably through simple immersion in a ferric nitrate (Fe(NO₃)₃) solution at room temperature. During this immersion process, the oxidation of the NF surface by NO₃^- ions increases the near-surface concentrations of OH^- and Ni²⁺, which results in the in situ deposition of a highly active amorphous Ni-Fe hydroxide (a-NiFeO_xH_y) layer. Specifically, the OER overpotential of the NF electrode decreases from 371 mV (bare NF) to 270 mV (@10 mA·cm^-2 in 0.1 M KOH) after immersion in a 20 mM Fe(NO₃)₃ solution for just 1 min. A longer immersion time results in further increased OER activity (196 mV@10 mA·cm^-2 in 1 M KOH). The overall water splitting properties of the a-NiFeO_xH_y@NF electrode were evaluated using a two-electrode configuration. It is worth noting that the current density can reach 25 mA·cm^-2 in 6 M KOH at an applied voltage of 1.5 V at room temperature.

The activity and durability of electrocatalysts are important factors in their practical applications, such as electrocatalytic oxygen evolution reactions (OERs) used in water splitting cells and metal–air batteries. In this study, a novel electrocatalyst, comprising few-layered graphitic carbon (~5 atomic layers) encapsulated heazlewoodite (Ni₃S₂@C) nanoparticles (NPs), was designed and synthesized using a one-step solid phase pyrolysis method. In the OER test, the Ni₃S₂@C catalyst exhibited an overpotential of 298 mV at a current density of 10 mA·cm^–2, a Tafel slope of 51.3 mV·dec^–1, and charge transfer resistance of 22.0 Ω, which were better than those of benchmark RuO₂ and most nickel-sulfide-based catalysts previously reported. This improved performance was ascribed to the high electronic conductivity of the graphitic carbon encapsulating layers. Moreover, the encapsulation of graphitic carbon layers provided superb stability without noticeable oxidation or depletion of Ni₃S₂ NPs within the nanocomposite. Therefore, the strategy introduced in this work can benefit the development of highly stable metal sulfide electrocatalysts for energy conversion and storage applications, without sacrificing electrocatalytic activity.

Electrocatalysts with high catalytic activity and stability play a key role in promising renewable energy technologies, such as fuel cells and metal-air batteries. Here, we report the synthesis of Fe/Fe₂O₃ nanoparticles anchored on Fe-N-doped carbon nanosheets (Fe/Fe₂O₃@Fe-N-C) using shrimp shell-derived N-doped carbon nanodots as carbon and nitrogen sources in the presence of FeCl₃ by a simple pyrolysis approach. Fe/Fe₂O₃@Fe-N-C obtained at a pyrolysis temperature of 1, 000 ℃ (Fe/Fe₂O₃@Fe-N-C-1000) possessed a mesoporous structure and high surface area of 747.3 m²·g^-1. As an electrocatalyst, Fe/Fe₂O₃@Fe-N-C-1000 exhibited bifunctional electrocatalytic activities toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media, comparable to that of commercial Pt/C for ORR and RuO₂ for OER, respectively. The Zn-air battery test demonstrated that Fe/Fe₂O₃@Fe-N-C-1000 had a superior rechargeable performance and cycling stability as an air cathode material with an open circuit voltage of 1.47 V (vs. Ag/AgCl) and a power density of 193 mW·cm^-2 at a current density of 220 mA·cm^-2. These performances were better than other commercial catalysts with an open circuit voltage of 1.36 V and a power density of 173 mW·cm^-2 at a current density of 220 mA·cm^-2 (a mixture of commercial Pt/C and RuO₂ with a mass ratio of 1:1 was used for the rechargeable Zn-air battery measurements). This work will be helpful to design and develop low-cost and abundant bifunctional oxygen electrocatalysts for future metal-air batteries.

A chitosan-polyvinyl alcohol (CS/PVA) co-polymer substrate possessing a large number of amino and hydroxyl groups is used as a substrate to induce the direct growth and in situ sequential transformation of titanate crystals under HF vapor phase hydrothermal conditions. The process involves four distinct formation/transformation stages. HTiOF₃ crystals with well-defined hexagonal shapes are formed during stage I, and are subsequently transformed into {001} faceted anatase TiO₂ crystal nanosheets during stage II. Interestingly, the formed anatase TiO₂ crystals are further transformed into cross-shaped and hollow squareshaped HTiOF₃ crystals during stages III and IV, respectively. Although TiO₂ crystal phases and facet transformations under hydrothermal conditions have been previously reported, in situ crystal transformations between different titanate compounds have not been widely reported. Such crystal formation/transformations are likely due to the presence of large numbers of amino groups in the CS/PVA substrate. When celluloses possessing only hydroxyl groups are used as a substrate, the direct formation of {001} faceted TiO₂ nanocrystal sheets is observed (rather than any sequential crystal transformations). This substrate organic functional group-induced crystal formation/transformation approach could be applicable to other material systems.

A pure rutile TiO₂ photoanode with 100% exposed pyramid-shaped (111) surfaces has been directly synthesized on a fluorine-doped tin oxide (FTO) conducting substrate via a facile one-pot hydrothermal method. The resulting rutile TiO₂ film on the FTO substrate possessed a film thickness of ca. 5 μm and showed good mechanical stability. After calcination at 450 ℃ for 2 h in argon (Ar), the fabricated rutile TiO₂ films with 100% exposed pyramid-shaped (111) surfaces were used as photoanodes, exhibiting excellent visible light photoelectrocatalytic activity toward oxidation of water and organics. The excellent visible light activity of the pure rutile TiO₂ film photoanode can be attributed to the Ti³⁺ doping in the bulk and high reactivity of the {111} crystal facets. Such a pure rutile TiO₂ film with highly reactive (111) surfaces is a promising material for visible light photocatalysis and solar energy conversion.