Visible light-driven the splitting of ethanol into hydrogen and acetaldehyde catalyzed by fibrous AgNPs/CdS hybrids at room temperature

Solar-Driven Biomass Reforming for Hydrogen Generation: Principles, Advances, and Challenges

Hydrogen (H2) has emerged as a clean and versatile energy carrier to power a carbon-neutral economy for the post-fossil era. Hydrogen generation from low-cost and renewable biomass by virtually inexhaustible solar energy presents an innovative strategy to process organic solid waste, combat the energy crisis, and achieve carbon neutrality. Herein, the progress and breakthroughs in solar-powered H2 production from biomass are reviewed. The basic principles of solar-driven H2 generation from biomass are first introduced for a better understanding of the reaction mechanism. Next, the merits and shortcomings of various semiconductors and cocatalysts are summarized, and the strategies for addressing the related issues are also elaborated. Then, various bio-based feedstocks for solar-driven H2 production are reviewed with an emphasis on the effect of photocatalysts and catalytic systems on performance. Of note, the concurrent generation of value-added chemicals from biomass reforming is emphasized as well. Meanwhile, the emerging photo-thermal coupling strategy that shows a grand prospect for maximally utilizing the entire solar energy spectrum is also discussed. Further, the direct utilization of hydrogen from biomass as a green reductant for producing value-added chemicals via organic reactions is also highlighted. Finally, the challenges and perspectives of photoreforming biomass toward hydrogen are envisioned.

Biochar-Based Photothermal Hydrogel for Efficient Solar Water Purification

The development of technology for solar interface evaporation has a significant meaning for the sustainable use of water resources in remote regions. However, establishing a solar evaporator with a high evaporation rate and favorable water treatment capabilities remains challenging. In this work, we reported a silver nanoparticle (AgNP)@carbonized cattail (CC)/polyvinyl alcohol (PVA) composite hydrogel (ACPH) membrane. Because of the successfully loaded AgNPs, which have a photothermal synergy with the CC, the ACPH-10 membrane obtained an excellent photothermal conversion performance. Additionally, the hydrophilicity of the ACPH-10 membrane ensures a sustainable water supply which is necessary for the improvement of the evaporation rate. Therefore, the ACPH-10 membrane achieves an evaporation rate of 1.66 kg m^-2 h^-1 and an efficiency of 88.0%, attributed to the remarkable photothermal conversion and water transmission. More importantly, the membrane exhibits superior purification ability in a variety of sewage. Pollutant removal rates in heavy metal and organic dye sewage have exceeded 99.8%. As a result, the ACPH membrane holds great promise for wastewater recovery and seawater desalination, which can aid in resolving the water crisis issue.

Cooperative Coupling of Oxidative Organic Synthesis and Hydrogen Production over Semiconductor-Based Photocatalysts

Merging hydrogen (H₂) evolution with oxidative organic synthesis in a semiconductor-mediated photoredox reaction is extremely attractive because the clean H₂ fuel and high-value chemicals can be coproduced under mild conditions using light as the sole energy input. Following this dual-functional photocatalytic strategy, a dreamlike reaction pathway for constructing C-C/C-X (X = C, N, O, S) bonds from abundant and readily available X-H bond-containing compounds with concomitant release of H₂ can be readily fulfilled without the need of external chemical reagents, thus offering a green and fascinating organic synthetic strategy. In this review, we begin by presenting a concise overview on the general background of traditional photocatalytic H₂ production and then focus on the fundamental principles of cooperative photoredox coupling of selective organic synthesis and H₂ production by simultaneous utilization of photoexcited electrons and holes over semiconductor-based catalysts to meet the economic and sustainability goal. Thereafter, we put dedicated emphasis on recent key progress of cooperative photoredox coupling of H₂ production and various selective organic transformations, including selective alcohol oxidation, selective methane conversion, amines oxidative coupling, oxidative cross-coupling, cyclic alkanes dehydrogenation, reforming of lignocellulosic biomass, and so on. Finally, the remaining challenges and future perspectives in this flourishing area have been critically discussed. It is anticipated that this review will provide enlightening guidance on the rational design of such dual-functional photoredox reaction system, thereby stimulating the development of economical and environmentally benign solar fuel generation and organic synthesis of value-added fine chemicals.

A new Ni-diaminoglyoxime-g-C3N4 complex towards efficient photocatalytic ethanol splitting via a ligand-to-metal charge transfer (LMCT) mechanism

We report a novel Ni-diaminoglyoxime-g-C₃N₄ (Ni-DAG-CN) complex for H₂ evolution through photocatalytic ethanol splitting. Compared to that of pristine g-C₃N₄, Ni-DAG-CN exhibits a 21-fold enhancement of photocatalytic activity (296.1 μmol h^-1 g^-1) under irradiation with excellent stability. The enhanced photocatalytic activity can be attributed to a proposed ligand-to-metal charge transfer (LMCT) mechanism, which is illustrated both experimentally and theoretically. This work provides great potential in the future design of low-cost, high-performance photocatalysts for H₂ evolution from alcohol splitting.

Design of C3 N4 -Based Hybrid Heterojunctions for Enhanced Photocatalytic Hydrogen Production Activity

Semiconductors and metals can form an Ohmic contact with an electric field pointing to the metal, or a Schottky contact with an electric field pointing to the semiconductor. If these two types of heterojunctions are constructed on a single nanoparticle, the two electric fields may cause a synergistic effect and increase the separation rate of the photogenerated electrons and holes. Metal Ni and Ag nanoparticles were successively loaded on the graphitic carbon nitride (g-C₃ N₄ ) surface by precipitation and photoreduction in the hope of forming hybrid heterojunctions on single nanoparticles. TEM/high-resolution TEM images showed that Ag and Ni were loaded on different locations on C₃ N₄ , which indicated that during the photoreduction reaction Ag⁺ obtained electrons from C₃ N₄ in the reduction reaction, whereas oxidation reactions proceeded on Ni nanoparticles. Photocatalytic hydrogen production experiments showed that C₃ N₄ -based hybrid heterojunctions can greatly improve the photocatalytic activity of materials. The possible reason is that two heterojunctions could form a long-range electric field similar to the p-i-n structure in semiconductors. Most of the photogenerated carriers were generated and then separated in this electric field, thereby increasing the separation rate of electrons and holes. This further improved the photocatalytic activity of C₃ N₄ .