Selective Photocatalytic Reduction of CO2 to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride.

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO2 ) and water (H2 O) into fuels and value-added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C3 N4 nanotubes (PCN) to form the photocatalyst Ag1 @PCN with Ag-N3 coordination for CO2 photoreduction using H2 O as the reductant. The as-synthesized Ag1 @PCN exhibits a high CO production rate of 0.32 µmol h-1 (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal-support interactions (Ag-N3 ) favor *CO2 adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C3 N4 and Ag single atoms, thereby accounting for the enhanced CO2 photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal-support interactions in enhancing the photoactivity and CO selectivity of CO2 photoreduction.

Photothermal synthesis of a CuO x &FeO y catalyst with a layered double hydroxide-derived pore-confined frame to achieve photothermal CO2 hydrogenation to CO with a rate of 136 mmol min-1 gcat -1.

Solar-driven CO2 conversion into the industrial chemical CO via the reverse water-gas reaction is an ideal technological approach to achieve the key step of carbon neutralization. The high reaction temperature is cost-free due to the photothermal conversion brought about by solar irradiation and is beneficial to the catalytic efficiency. However, the thermostability of adopted catalysts is a great challenge. Herein, we develop an in situ photothermal synthesis to obtain a CuO x &FeO y catalyst with a layered double hydroxide-derived pore-confined frame. The optimized sample delivers a CO generation rate of 136.3 mmol min-1 gcat -1 with the selectivity of ∼100% at a high reaction temperature of 1015 °C. The efficient catalytic activity can be attributed to the fact that the pore-confined frame substrate prevents the growth of CuO x and FeO y nanoparticles during the high-temperature reaction and the basic groups on the substrate promote the adsorption and activation of CO2.

Structural and Componential Engineering of Co2P&CoP@N-C Nanoarrays for Energy-Efficient Hydrogen Production from Water Electrolysis.

The development of electrocatalysts for efficient water splitting is a pivotal and challenging task. Transition-metal phosphides (TMPs) have been known as one of the most promising candidates for the efficient hydrogen evolution reaction (HER) due to their favorable intrinsic reactivity. However, structural engineering related to the gas bubbles evolution and tiny regulation of components concerned with the electronic structure remained as a significant challenge that requires further optimization. Herein, the nanoarrays (NAs) composed of ultrasmall Co2P and CoP nanoparticle-embedded N-doped carbon matrix (Co2P&CoP@N-C) are prepared and demonstrated an overpotential of 62.8 ± 4.7 mV at 10 mA cm-2 in 1.0 M KOH. The nanoarray-structured electrocatalyst revealed the superaerophobicity and facilitates the detachment of the in situ formed hydrogen gas bubbles, ensuring abundant catalytic sites and electrode-electrolyte interface for the mass transfer process. The amount of P doping modulated the local electron density around Co and P atoms, which attains a favorable compromise to afford sufficient electrons for the electrocatalysis and inhibit the negative influence of H2 desorption. Significantly, the lowered overpotential induced by the electrocatalyst surface architecture is much stronger than that of the component content and promotes the electrocatalytic activity.

Cost-Efficient Photovoltaic-Water Electrolysis over Ultrathin Nanosheets of Cobalt/Iron-Molybdenum Oxides for Potential Large-Scale Hydrogen Production.

Unassisted photovoltaic (PV) water splitting to hydrogen system is of great potential for future environmental-friendly fuel production from renewable solar energy. However, industrialization simultaneously requires higher efficiency, sustained stability and a lower cost for the system. In this work, the ultrathin cobalt/iron-molybdenum oxides nanosheet on nickel foam (NF) is prepared for efficient HER and OER, respectively, delivering a relatively low voltage of 1.45 V at 10 mA cm-2 in two-electrodes configuration. Water electrolysis at low voltage driven by electrocatalysts is critical for realizing energy conversion. Integrated with a commercial monocrystalline silicon cell, the H2 area specific activity of 0.47 L m-2 h-1 is achieved with a solar-to-hydrogen efficiency of 15.1% under solar simulator illumination (100 mW cm-2 ) and no performance degradation appeares over 160 h. Such a solar conversion technology demonstrates the potential for long-term and cost-efficient H2 production in large-scale industrialization and provides an exploration for new-type of energy-conversion system.

Designing Carbonized Loofah Sponge Architectures with Plasmonic Cu Nanoparticles Encapsulated in Graphitic Layers for Highly Efficient Solar Vapor Generation.

Solar vapor generation represents a promising approach to alleviate water shortage for producing fresh water from undrinkable water resources. Although Cu-based plasmonics have attracted tremendous interest due to efficient light-to-heat conversion, their application faces great challenges in the oxidation resistance of Cu and low evaporation rate. Herein, a hybrid of three-dimensional carbonized loofah sponges and graphene layers encapsulated Cu nanoparticles is successfully synthesized via a facile pyrolysis method. In addition to effective light harvesting, the localized heating effect of stabilized Cu nanoparticles remarkably elevated the surface temperature of Cu@C/CLS to 72 °C, and a vapor generation rate as high as 1.54 kg m-2 h-1 with solar thermal efficiency reaching 90.2% under 1 Sun illumination was achieved. A study in the purification of sewage and muddy water with Cu@C/CLS demonstrates a promising perspective in a practical application. These results may offer a new inspiration for the design of efficient nonprecious Cu-based photothermal materials.