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Photocatalytic syngas (CO and H2) production with CO2 as gas source not only ameliorates greenhouse effect, but also produces valuable chemical feedstocks. However, traditional photocatalytic systems require noble metal or suffers from low yield. Here, we demonstrate that S vacancies ZnIn2S4 (VS‐ZnIn2S4) nanosheets are an ideal photocatalyst to drive CO2 reduction into syngas. It is found that building S vacancies can endow ZnIn2S4 with stronger photoabsorption, efficient electron–hole separation, and larger CO2 adsorption, finally promoting both hydrogen evolution reaction (HER) and CO2 reduction reaction (CO2RR). The syngas yield of CO and H2 is therefore significantly increased. In contrast to pristine ZnIn2S4, the syngas yield over VS‐ZnIn2S4 can be improved by roughly ≈4.73 times and the CO/H2 ratio is modified from 1:4.18 to 1:1. Total amount of syngas after 12 h photocatalysis is as high as 63.20 mmol g−1 without use of any noble metals, which is even higher than those of traditional noble metal‐based catalysts in the reported literatures. This work demonstrates the critical role of S vacancies in mediating catalytic activity and selectivity, and highlights the attractive ability of defective ZnIn2S4 for light‐driven syngas production. [ABSTRACT FROM AUTHOR]

Current heterojunction photocatalysts suffer from sluggish charge transfer due to the discontinuous interfaces at an atomic level. Herein, we report a NiO–Co 3 O 4 ultrathin lateral heterojunction using NiCo-based bimetal–organic layers as precursors. The atomic-resolution images display a unique continuous semi-coherent interface between NiO and Co 3 O 4. The experimental results confirm that the continuous semi-coherent interfaces effectively expedite the electron transfer from NiO to Co 3 O 4. Concomitantly, the electron transfer raises d -band center of Co 3 O 4 in NiO–Co 3 O 4 toward Fermi level, as revealed by the density functional theory calculations. As a result, the *COOH intermediate can be strongly bound on cobalt reactive centers. The successful modulation of charge transfer and intermediate binding by continuous semi-coherent interfaces leads to a remarkable gas yield of 22.67 mmol h−1 from photocatalytic CO 2 reduction over NiO–Co 3 O 4. This work highlights the crucial roles of interface engineering in regulating carrier kinetics and surface reactions. [Display omitted] • Bimetal–organic layer-derived NiO–Co 3 O 4 ultrathin lateral heterojunction. • A unique continuous semi-coherent interface at an atomic level. • The continuous interface accelerates electron transfer from NiO to Co 3 O 4. • The continuous interface raises d -band center toward Fermi level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Upcycling of waste adsorbents into CO 2 -reduction photocatalysts. • Harmful heavy metals are removed and transformed into valuable photocatalysts. • In situ formation of metal sulfides semiconductors through sulfurization treatment. • An ideal adsorbent of one-unit-cell calcium silicate hydrate ultrathin nanosheets. Although adsorption is regarded as a facile and efficient method to remove heavy metals from polluted water, the disposal of the spent adsorbents remains a great challenge. Here, an "adsorbent-to-photocatalyst" conversion strategy is reported. One-unit-cell calcium silicate hydrate (CSH) nanosheets (~2.8 nm) are used as an ideal adsorbent, and four typical heavy metals including Cu2+, Zn2+, Co2+, and Cd2+ ions are selected for studies. CSH nanosheets show superiority in the ultrahigh specific surface area (577.8 m2 g−1) and chemical stability. After the heavy metal removal, the CSH nanosheets containing heavy metal ions are transformed into metal sulfides through in situ sulfurization treatment. Interestingly, in the case of Cd2+ ions, CdS nanoparticles are produced and well dispersed on the surface of CSH nanosheets. CSH-CdS has a narrow bandgap of 2.34 eV and shows the photoabsorption edge up to visible light (550 nm). Besides, CSH-CdS also possesses a suitable energy band structure, making itself an ideal photocatalyst for CO 2 reduction under visible light (λ > 420 nm). The "adsorbent-to-photocatalyst" conversion strategy demonstrated here not only ameliorates the water and air pollution but also produces the valuable chemical feedstock (CO and H 2). [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrostatic self-assembly of the 2D/2D NiAl-LDH/silicate composite. • Suppressing the restacking of NiAl-LDH nanosheets by silicate nanosheets. • The rapid charge transfer of the NiAl-LDH/silicate composite. • Efficient photocatalytic CO 2 reduction over the NiAl-LDH/silicate composite. The layered double hydroxide (LDH) nanosheets are ideal for photocatalytic CO 2 reduction. How to suppress the spontaneous agglomeration of LDH remains a challenge. Herein, this work reports that the insulated calcium silicate hydrate (CSH) nanosheets effectively suppress the agglomeration of NiAl-LDH nanosheets by an electrostatic self-assembly. The charge transfer of NiAl-LDH/CSH is effectively promoted, as verified by photoelectrochemical characterizations. As a result, the CO and H 2 generation rates from photocatalytic CO 2 reduction are as high as 3432 and 1411 μmol g−1h−1, which are ∼2.4 times higher than that of the pure NiAl-LDH. [ABSTRACT FROM AUTHOR]

The activity of photocatalytic CO 2 reduction (PCR) remains inadequate due to the thermodynamically stable CO 2 molecules and sluggish carrier kinetics. This work simultaneously adopts active site and heterojunction engineering to collaboratively enhance PCR. A heterojunction of g-C 3 N 4 microtube-supported Co 3 O 4 nanoparticle has been developed through the hydrothermal pretreatment and calcination processes. The g-C 3 N 4 microtubes play dual roles in enhancing PCR of Co 3 O 4 : (1) they act as a substrate to support Co 3 O 4 nanoparticles, thereby making small size and good dispersion of Co 3 O 4 nanoparticles. The Co active sites can be highly exposed to accept photogenerated electrons and capture CO 2 molecules; and (2) the p-type Co 3 O 4 nanoparticles and n-type g-C 3 N 4 microtubes build a p–n junction. An internal electric field is created to expedite the charge transfer. As a result, the g-C 3 N 4 microtube-supported Co 3 O 4 nanoparticle affords a significantly high turnover number (TON) of 24.72, which is 24-fold higher than that of the pure Co 3 O 4 and comparable to state-of-the-art photocatalysts. [Display omitted] • Active site and heterojunction engineering enable the enhanced CO 2 photoreduction. • A hollow tubular heterojunction of g-C 3 N 4 microtubes@Co 3 O 4 nanoparticles. • Photosensitizer/heterojunction hybrid systems with a high turnover number. • The strong CO 2 adsorption and rapid electron transfer. [ABSTRACT FROM AUTHOR]

[Display omitted] • A tree-inspired semiconductor-on-ceramic 2D/1D heterostructure. • Vertical alignment of silicate nanosheets on hydroxyapatite nanowires. • Hierarchical structure enhances CO 2 adsorption and charge transfer. • Highly efficient CO 2 photoreduction into CO. Two-dimension nanosheets are ideal photocatalysts for CO 2 reduction due to their high exposure of active sites and short charge transfer pathway. However, 2D photocatalysts have a tendency to agglomeration, thus compromising the performance of photocatalytic CO 2 reduction. Trees, one of the most important plants for photosynthesis, have a unique "leaf-on-branch" structure. This unique two-dimension/one-dimension (2D/1D) configuration maximizes the adsorption of CO 2 molecules and light harvesting. Herein, a tree-inspired semiconductor-on-ceramic 2D/1D heterostructure for efficient photocatalytic CO 2 reduction is reported. The cobalt silicate (CoSi) nanosheets (∼0.68 nm) are in situ grown on the surfaces of hydroxyapatite (HAP) nanowires, creating a well-defined 2D/1D hierarchical structure. The vertical alignment of ultrathin CoSi nanosheets on the HAP nanowires effectively suppresses their agglomeration, leading to a large BET surface area (106.45 m2/g) and excellent CO 2 adsorption (8.00 cm3 g−1). The results of photoelectrochemical characterization demonstrate that the 2D/1D hierarchical structure is powerful to expedite charge transfer. As a result, the gas generation rate of CO is as high as 28780 μmol g−1 h−1 over the CoSi-on-HAP 2D/1D heterostructure. In addition, the electron transfer mechanism and reaction pathways of CO 2 reduction are revealed by in situ irradiated XPS and in situ DRIFT spectra. [ABSTRACT FROM AUTHOR]

• Recycling harmful heavy metals for photocatalytic CO 2 reduction. • Proposing an "adsorbent-to-photocatalyst" strategy. • Calcium silicate hydrate ultrathin nanosheets as an ideal adsorbent. • A new semiconductor nickel silicate hydroxide is produced spontaneously. Polluted water and exhaust gas released from industrial activities cause a series of environmental issues such as heavy metals accumulation and greenhouse effect. Here, we have proposed an "adsorbent-to-photocatalyst" conversion strategy to bridge water remediation with photocatalytic CO 2 reduction. Harmful heavy metals in polluted water are removed and collected by adsorbents, which are converted into valuable photocatalysts for CO 2 reduction without secondary treatment. Calcium silicate hydrate (CSH) nanosheets are prepared as an ideal "bridge". Their ultrathin thickness (2.8 nm), ultrahigh surface area (637.2 m2 g−1), and abundant surface hydroxyls are much favorable for both heavy metals removal and photocatalysis processes. Four typical heavy metals including Cu2+, Zn2+, Ni2+, and Pb2+ are selected for studies. Interestingly enough, in the case of Ni2+ removal, CSH nanosheets undergo phase change and they are spontaneously converted into a new semiconductor nickel silicate hydroxide. The nickel silicate hydroxide has a suitable energy level for reducing CO 2 into CO. And its strong CO 2 adsorption and abundant exposed Ni2+ sites contribute to efficient and selective photocatalytic CO 2 reduction. The CO yield is up to 1.71 × 104 μmol g−1 h−1 with 99.2% selectivity under visible light. [ABSTRACT FROM AUTHOR]