Kinetically and Thermodynamically Favorable Ni-Al Layered Double Hydroxide/Ni-Doped Zn0.5Cd0.5S S-Scheme Heterojunction Triggering Photocatalytic H2 Evolution.

Layered double hydroxide (LDH)-based photocatalysts have attracted more attention in photocatalysis due to their low cost, wide band gaps, and adjustable photocatalytic active sites; however, their low photogenerated carrier separation efficiency limits their photocatalytic efficiency. Herein, a NiAl-LDH/Ni-doped Zn0.5Cd0.5S (LDH/Ni-ZCS) S-scheme heterojunction is rationally designed and constructed from kinetically and thermodynamically favorable angles. The 15% LDH/1% Ni-ZCS displays comparable photocatalytic hydrogen evolution (PHE) activity with a rate of 6584.0 µmol g-1 h-1, which exceeds by ∼6.14- and ∼1.73-fold those of ZCS and 1% Ni-ZCS, respectively, and outperforms most of the previously reported LDH-based and metal sulfide-based photocatalysts. In addition, the apparent quantum yield of 15% LDH/1% Ni-ZCS reaches 12.1% at 420 nm. In situ X-ray photoelectron spectroscopy, photodeposition, and theoretical calculation reveal the specific transfer path of photogenerated carriers. On this basis, we propose the possible photocatalytic mechanism. The fabrication of the S-scheme heterojunction not only accelerates the separation of photogenerated carriers but also decreases the activation energy of H2 evolution and improves the redox capacity. Moreover, there are huge amounts of hydroxyl groups distributed on the surface of photocatalysts, which is highly polar and easy to combine with H2O with a large dielectric constant to form a hydrogen bond, which can further accelerate PHE.

Interior and Surface Synergistic Modifications Modulate the SnNb2O6/Ni-Doped ZnIn2S4 S-Scheme Heterojunction for Efficient Photocatalytic H2 Evolution.

Interior and surface synergistic modifications can endow the photocatalytic reaction with tuned photogenerated carrier flow at the atomic level. Herein, a new class of 2D/2D SnNb2O6/Ni-doped ZnIn2S4 (SNO/Ni-ZIS) S-scheme heterojunctions is synthesized by a simple hydrothermal strategy, which was used to evaluate the synergy between interior and surface modifications. Theoretical calculations show that the S-scheme heterojunction boosts the desorption of H atoms for rapid H2 evolution. As a result, 25% SNO/Ni0.4-ZIS exhibits significantly improved PHE activity under visible light, roughly 4.49 and 2.00 times stronger than that of single ZIS and Ni0.4-ZIS, respectively. In addition, 25% SNO/Ni0.4-ZIS also shows superior structural stability. This work provides advanced insight for developing high-performance S-scheme systems from photocatalyst design to mechanistic insight.

Boosting H2 Production over C60 -Mediated NH2 -MIL-125(Ti)/Zn0.5 Cd0.5 S S-Scheme Heterojunction via Enhanced Interfacial Carrier Separation.

Improving greatly the separation efficiency of interfacial charge carrier is a major challenge in photocatalysis. Herein, a new class of C60 -mediated NH2 -MIL-125(Ti)/Zn0.5 Cd0.5 S S-scheme heterojunction with enhanced interfacial charge carrier separation is designed and synthesized. The constructed S-scheme heterojunction thermodynamically favors photocatalytic H2 evolution because of the large driving force resulting from its strong redox abilities. As a consequence, the optimum proportion of C60 -mediated NH2 -MIL-125(Ti)/Zn0.5 Cd0.5 S S-scheme heterojunction displays comparable H2 evolution activity with a rate of 7825.20 µmol h-1 g-1 under visible light irradiation, which is about 93.05 times, 6.38 times and 2.65 times higher than that of 2% C60 /NH2 -MIL-125(Ti), Zn0.5 Cd0.5 S and 45% NH2 -MIL-125(Ti)/Zn0.5 Cd0.5 S, and outperforms the majority of the previously reported MOFs-based photocatalysts. Spectroscopic characterizations and theory calculations indicate that the S-scheme heterojunction can powerfully promote the separation of photogenerated carriers. This work offers a new insight for future design and development of highly active MOFs-based photocatalysts.

Challenges in Photocatalytic Carbon Dioxide Reduction.

An energy crisis and significant anthropogenic CO2 emissions as a result of rising fossil fuel consumption have caused a rapid increase in global temperature. One of the best solutions to these two issues is thought to be the photocatalytic reduction of CO2 into value-added carbon-containing products. In this aspect, the main challenges mainly include the photocatalytic mechanism, reaction activity, and product selectivity, especially in ambiguous reaction pathways and product selectivity, an unclear charge transfer mechanism, and an overestimate of product yield. Therefore, in this perspective, we attempt to exhibit the discussion and in-depth analysis of the possible reaction pathways and product selectivity, the specific charge transfer mechanism, and the origin of carbon-containing products in phtocatalytic CO2 reduction. Besides, the fundamentals for photocatalytic CO2 reduction are also illustrated. Finally, the state-of-the-art challenges and perspectives in CO2 photoreduction are highlighted and discussed in detail. This perspective is expected to evoke more research attention for the photocatalytic reduction of CO2 into value-added products.

Correction: Critical role of hydrogen bonding between microcrystalline cellulose and g-C3N4 enables highly efficient photocatalysis.

Correction for 'Critical role of hydrogen bonding between microcrystalline cellulose and g-C3N4 enables highly efficient photocatalysis' by Zhaoqiang Wang et al., Chem. Commun., 2024, 60, 204-207, https://doi.org/10.1039/D3CC04800D.

Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like NiAl-LDH microspheres with Z-scheme for significantly enhanced CO2 photoreduction into CO.

The conversion of carbon dioxide (CO2) into value-added C1 and/or C2 chemicals by photocatalytic technology has been regarded as a "one stone-two birds" solution for environmental degradation and energy shortage. In this work, a novel Z-scheme mechanism photocatalyst of Ag-modified α-Fe2O3 spherical particles interspersed on hierarchical flower-like layered nickel-aluminum hydroxides (NiAl-LDH) microspheres (α-Fe2O3/Ag/NiAl-LDH, designated as FALDH) is successfully prepared by a combined in-situ hydrothermal and grating strategy. As expected, the optimal sample of FALDH-5/10 exhibits significantly enhanced photocatalytic performance for CO2 reduction with a highest CO yield up to 46.7 µmol g-1 under simulated sunlight without any sacrificial reagents and photosensitizers, compared with the pristine NiAl-LDH, binary Ag/NiAl-LDH and α-Fe2O3/NiAl-LDH, as well as surpassing the previously reported LDH-based counterparts. The high activity is ascribed to strong interaction between the NiAl-LDH microspheres and highly-dispersed Ag/α-Fe2O3 particles, boosted CO2 adsorption capacity and optimized bandgap from α-Fe2O3, and increased utilization efficiency of light from Ag. This study offers a new idea for more efficient stimulating the photocatalytic activity of LDHs by the construction of Z-scheme heterojunction with the aid of plasmonic metal(s) for CO2 photoreduction, and is expected to be employed to other photocatalytic applications effectively.

Size effect of ruthenium nanoparticles on water cracking properties with different crystal planes for boosting electrocatalytic hydrogen evolution.

Small size ruthenium (Ru) nanoparticles have shown remarkable potential for electrocatalytic hydrogen evolution reaction (HER). Nevertheless, the complicated preparation and relatively low activity of small size Ru nanoparticles are two key challenges. In this work, carbon nanotubes supported Ru nanoparticles catalysts (cnts@NC-Ru t °C) with different sizes were prepared via using the combination of L-3,4-dihydroxyphenylalanine (l-dopa) self-polymerization oxidation reaction and different high temperature annealing to study the variation of particle activity with size. Electrochemical test results showed that the optimized cnts@NC-Ru 700 °C catalyst exhibited a very low overpotential at 10 mA/cm2 (21 mV) and tafel slope of 34.93 mV/dec when the mass loading of precious metal per unit area was merely 12.11 µg/cm2 that surpassed most recently reported high-performance Ru based catalyst. The results of density functional theory (DFT) calculation showed that small Ru nanoparticles had abundant active sites, and the H2O dissociation on small Ru nanoparticles (110) surface is quite easy than other surfaces, while (111) surface of small Ru nanoparticles is beneficial for Tafel step of HER. The synergy between (110) and (111) surfaces on the Ru cluster contributes to its outstanding HER performance. This study provides a novel design idea in promoting the preparation method and uncovering the reason of high activity of small size Ru nanoparticles.

Recent Advances in LDH/g-C3N4 Heterojunction Photocatalysts for Organic Pollutant Removal.

Environmental pollution has been decreased by using photocatalytic technology in conjunction with solar energy. An efficient method to obtain highly efficient photocatalysts is to build heterojunction photocatalysts by combining graphitic carbon nitride (g-C3N4) with layered double hydroxides (LDHs). In this review, recent developments in LDH/g-C3N4 heterojunctions and their applications for organic pollutant removal are systematically exhibited. The advantages of LDH/g-C3N4 heterojunction are first summarized to provide some overall understanding of them. Then, a variety of approaches to successfully assembling LDH and g-C3N4 are simply illustrated. Last but not least, certain unmet research needs for the LDH/g-C3N4 heterojunction are suggested. This review can provide some new insights for the development of high-performance LDH/g-C3N4 heterojunction photocatalysts. It is indisputable that the LDH/g-C3N4 heterojunctions can serve as high-performance photocatalysts to make new progress in organic pollutant removal.

Critical role of hydrogen bonding between microcrystalline cellulose and g-C3N4 enables highly efficient photocatalysis.

Developing a highly efficient photocatalyst for energy and environmental applications is urgently required. Herein, graphitic carbon nitride (CN) coupled with microcrystalline cellulose (MCC) (denoted as MCC-X/CN) shows excellent photocatalytic performance for tetracycline (TC) degradation and H2 evolution. And the optimized MCC-0.05/CN shows an improved TC degradation rate (Kapp = 0.019 min-1) and H2 evolution rate (642.71 µmol g-1 h-1), which are 1.9 and 22 times higher than those of pure CN, respectively. This improvement primarily results from hydrogen bonding (H-bonding) between CN and MCC, which enables excellent charge separation and migration, leading to the outstanding photoelectrochemical properties of MCC-0.05/CN.

Bridging between NiAl-LDH and g-C3N4 by using carbon quantum dots for highly enhanced photoreduction of CO2 into CO.

A series of treble NiAl-LDH/g-C3N4/carbon quantum dots (LDH/CN/CQDs) photocatalysts is successfully prepared for the photoreduction of CO2 to CO via a facile hydrothermal pathway. In the 3D flower-like LDH/CN/CQDs, CQDs not only achieve the efficient inhibition of charge recombination but also act as the unhindered "electronic bridges" to synergistically construct a classical type-Ⅱ charge transfer configuration, which synchronously permits the effluence of photogenerated electrons from CN to LDH and holes from LDH to CN, and promotes ultraviolet-visible irradiation respondence. The sample of LDH/CN/CQDs-6 is the optimal one amongst the LDH/CN/CQDs with a larger special surface area (98.43 m2g-1) and an appropriate content of CQDs (66.9 wt%), exhibiting the highest CO evolution rate (5.2 µmol·g-1·h-1) under visible light irradiation without any sacrificial agent or photosensitizer in water. This is 26.8- and 20.9-fold higher than those of the pristine LDH, pure CN, and their binary counterparts, respectively, and also outperforms most reported LDH-based photocatalysts. As unhindered electron conduction bridges, the highly dispersed CQDs in the LDH/CN heterojunction significantly increase utilization efficiency of light energy and separation efficiency of photogenerated electron-hole pairs. This work provides a beneficial attempt to integrate CQDs with LDH/CN for the positive synergetic effect on both photoelectric properties and electron transfer to obtain highly enhanced photocatalytic activity of CO2 into CO, and expected to be extended towards broader photocatalytic applications.