The S‐scheme heterojunctions have great potential for photocatalytic carbon dioxide reduction due to their unique carrier migration pathways, superior carrier separation efficiencies, and high redox capacities. However, the precise process of the oriented powerful electron transport remains a great challenge. Herein, an InOCd bond‐modulated S‐scheme heterojunction of In2O3/CdSe‐DETA is synthesized by a simple microwave‐assisted hydrothermal method for the accelerated photogenerated electron transfer. Meanwhile, the oxygen vacancies (Vo) of In2O3 have an electron capture effect. Consequently, thanks to the synergistic effect of this In‐Vo‐In‐O‐Cd structural units at the interface, electrons are extracted and rapidly transferred to the surface‐active sites, which improves the electronic coupling of CO2. This finding precisely adjusts the electron transfer pathway and shortens the electron transfer distance. The synergistic effect of this chemical bond established in the S‐scheme heterostructure with oxygen vacancies in In2O3 (Vo‐In2O3) provides new insights into photocatalytic CO2 reduction.

Interfacial Chemical Bond and Oxygen Vacancy‐Enhanced In2O3/CdSe‐DETA S‐scheme Heterojunction for Photocatalytic CO2 Conversion

Single/dual-metal atoms supported on carbon matrix can be modulated by coordination structure and neighboring active sites. Precisely designing the geometric and electronic structure and uncovering the structure-property relationships of single/dual-metal atoms confront with grand challenges. Herein, this review summarizes the latest progress in microenvironment engineering of single/dual-atom active sites via a comprehensive comparison of single-atom catalyst (SACs) and dual-atom catalysts (DACs) in term of design principles, modulation strategy, and theoretical understanding of structure-performance correlations. Subsequently, recent advances in several typical electrocatalysis process are discussed to get general understanding of the reaction mechanisms on finely-tuned SACs and DACs. Finally, full-scaled summaries of the challenges and prospects are given for microenvironment engineering of SACs and DACs. This review will provide new inspiration on the development of atomically dispersed catalysts for electrocatalytic application. This article is protected by copyright. All rights reserved.

Microenvironment Engineering of Single/Dual-atom Catalysts for Electrocatalytic Application.

Lead halide perovskites MAPbX3 (MA = CH3NH3 or Cs; X = I, Br, Cl) are well considered to be potential candidates for photocatalytic reaction due to its excellent photoelectrical properties, but they still suffer from the low charge separation efficiency and slow catalytic reaction dynamics. To tackle the drawbacks, herein, MAPbBr3/carbon sphere (CS) composite photocatalysts using glucose as the carbon source were elaborately designed and fabricated via a dry mechanochemical grinding process. The interfacial interaction Pb-O-C chemical bonds were constructed between MAPbBr3 and the carbon sphere surface containing organic functional groups. By optimizing the content of CSs, the enhanced photocatalytic degradation kinetic rate of Malachite Green (MG) pollutants (92% within 20 min) for MAPbBr3/CSx (x = 17 wt.%) is about 3.6-fold of that for pristine MAPbBr3, which is attributed to the corporative adsorption and enhanced carrier transportation and separation of MAPbBr3/CSx. Furthermore, the possible degradation mechanism was proposed on basis of the electrochemical, mass spectrometry and optical characterization results. Owing to the robust interfacial interaction, effective electron extraction rate (ket = 4.6 × 107 sec−1) from MAPbBr3 to CS can be established, which driven oxygen activation where superoxide radicals (•O2−) played an important role in MG degradation. It is expected that mechanochemistry strategy may provide a new route to design efficient lead halide perovskite-carbon or metal oxide or sulfide composite photocatalysts.

Mechanochemical synthesis of MAPbBr3/carbon sphere composites for boosting carrier-involved superoxide species.

Oxygen vacancy engineering of zinc oxide for boosting piezo-electrocatalytic hydrogen evolution

The solar-driven evolution of hydrogen from water using particulate photocatalysts is considered one of the most economical and promising protocols for achieving a stable supply of renewable energy. However, the efficiency of photocatalytic water splitting is far from satisfactory due to the sluggish electron-hole pair separation kinetics. Herein, isolated Mo atoms in a high oxidation state have been incorporated into the lattice of Cd0.5Zn0.5S (CZS@Mo) nanorods, which exhibit photocatalytic hydrogen evolution rate of 11.32 mmol g-1 h-1 (226.4 µmol h-1; catalyst dosage 20 mg). Experimental and theoretical simulation results imply that the highly oxidized Mo species lead to mobile-charge imbalances in CZS and induce the directional photogenerated electrons transfer, resulting in effectively inhibited electron-hole recombination and greatly enhanced photocatalytic efficiency.

Isolated Electron Trap-Induced Charge Accumulation for Efficient Photocatalytic HydrogenProduction.

Photoreduction of CO 2 to C 2+ solar fuel is a promising carbon-neutral technology for renewable energy. This strategy is challenged by its low productivity due to low efficiency in multielectron utilization and slow C-C coupling kinetics. This work reports a dual-metal photocatalyst consisted of atomically dispersed Indium-Copper anchored on polymeric carbon nitride (InCu/PCN), on which the photoreduction of CO 2 delivered an excellent ethanol production rate of 28.5 μmol·g -1 ·h -1 with a high selectivity of 92%. Coupled experimental investigation with DFT calculation, this study unveils the following mechanisms underpinning the high performance of this catalyst. Essentially, In-Cu interaction enhances the charge separation by accelerating charge transfer from PCN to metal sites. In also transfers electrons to neighboring Cu via Cu-N-In bridges, increasing the electron density of Cu active sites. Furthermore, In-Cu dual-metal sites promote the adsorption of *CO intermediates and lower the energy barrier of C-C coupling.

Atomically Dispersed Indium-Copper Dual-Metal Active Sites Promoting C-C Coupling for CO2 Photoreduction to Ethanol.

Relaxation pathways of upper excited electronic states of malachite green (MG) in ethanol and in films are studied by steady-state and time-resolved spectroscopic techniques. In contrast to ethanol...

Upper Excited State Photophysics of Malachite Green in Solution and Films.

The thermal adsorption residue (TDR) from oil sludge co-contaminated soil was employed to remove As(III), Zn(II), Cu(II), Cd(II) in aqueous solution. The results showed that the TDR could efficiently neutralize the acid and adapt to the extensive pH. The adsorption of four heavy metals on TDR could be divided into three stages. The maximum adsorption capacity were 86.59, 249.07, 339.88, 322.86 mg·g−1 for As(III), Zn(II), Cu(II), Cd(II), respectively. The coexistence of Zn(II)/Cu(II)/Cd(II) could promote As(III) removal but As(III) led to decreasing of Zn(II)/Cu(II)/Cd(II) adsorption capacity in binary system. There was a significant competitive adsorption on TDR among the three cations which followed the selectivity sequence of Cu(II)>Zn(II)>Cd(II). The SEM-EDS, XRD, FTIR and XPS analyses demonstrated that the As(III) was removed via formation of Ca-As precipitation, and the Zn(II), Cu(II), Cd(II) were removed through precipitating as hydroxides/carbonates/silicates combining with ion exchange. Specially, the Cu(II) mainly precipitated in the form of Cu4(SO4)(OH)6⋅2H2O and Cu4(OH)6SO4 under sulfuric acid solution environment. Overall, this study indicates the potential of TDR as a cost-effective adsorbent in acid heavy metals contaminated wastewater treatment. 

Highly efficient removal of As(III), Zn(II), Cu(II) and Cd(II) in aqueous solution using thermal desorption residue from oil sludge contaminated soil: Performance and mechanism

With the aim of constructing efficient photoelectric organic materials, a pyrido[3,2-g]quinoline derivative named LA17b has been synthesized, and its photodynamic relaxation processes in solvents and films were studied by time-resolved fluorescence and femtosecond transient absorption techniques. The steady-state fluorescence spectra show pronounced red-shift with the increase of the solvent polarity as well as in binary solvent hexane/ethanol by increasing ethanol concentration. However, the strong red-shift does not lead to quenching of the fluorescence. This is explained in terms of a twisted intramolecular charge transfer (TICT) state. The TICT state of LA17b in ethanol is highly emissive with a long fluorescence lifetime: 1.1 ns. TICT state was shown to play an important role in enhancement of intersystem crossing rate. TD-DFT calculations confirm the pathways of relaxation of locally excited state via TICT and triplet states. In films, the photodynamic properties are similar to that of LA17b in hexane and the TICT state vanishes due to the rigid environment. The obtained optical properties of this molecule suggest that it can be a promising candidate for various optoelectronic applications.

Yichen Zhou

Papers

Atomically Dispersed Indium-Copper Dual-Metal Active Sites Promoting C-C Coupling for CO2 Photoreduction to Ethanol.

Upper Excited State Photophysics of Malachite Green in Solution and Films.

Highly efficient removal of As(III), Zn(II), Cu(II) and Cd(II) in aqueous solution using thermal desorption residue from oil sludge contaminated soil: Performance and mechanism

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer.

Singlet Fission from Upper Excited States of Bodipy Crystalline Film and Single Crystal