Conversion of Biomasses and Copper into Catalysts for Photocatalytic CO2 Reduction

Crystal OH mediating pathway for hydrogen peroxide production via two-electron water oxidation in non-carbonate electrolytes

Water oxidation presents a promising avenue for hydrogen peroxide (H2O2) production. However, the reliance on alkaline bicarbonate electrolytes as an intermediate has limitations, such as H2O2 decomposition and a narrow pH effectiveness range (7-9), restricting its utility across wider pH ranges. This study unveils a crystal OH mediating pathway that stabilizes SO4OH* as a crucial intermediate. Basic copper carbonate (Cu2(OH)2CO3) tablets, commonly found on cultural relics, exhibit the capability to generate H2O2 in neutral or acidic non-bicarbonate electrolytes. By leveraging this crystal OH mediating strategy, considerable H2O2 production in Na2SO4 electrolytes is achievable. Notably, the H2O2 production rate can reach 64.35 μmol h-1 at 3.4 V vs. RHE in a 50 mL 0.5 M Na2SO4 electrolyte. This research underscores the importance of crystal part in catalyst in catalyzing the 2e- water oxidation reaction, offering valuable insights for future investigations.

Copper-Nanoparticle-Decorated Hydrothermal Carbonaceous Carbon-Polydimethylsiloxane Nanocomposites: Unveiling Potential in Simultaneous Light-Driven Interfacial Water Evaporation and Power Generation

This study introduces a hydrothermal synthesis method that uses glucose and Cu2+ ions to create a Cu-nanoparticle (NP)-decorated hydrothermal carbonaceous carbon hybrid material (Cu-HTCC). Glucose serves both as a reducing agent, efficiently transforming Cu2+ ions into elemental Cu nanostructures, and as a precursor for HTCC microstructures. An enhanced plasmon-induced electric field resulting from Cu NPs supported on microstructure matrices, coupled with a distinctive localized π-electronic configuration in the hybrid material, as confirmed by X-ray photoelectron spectroscopic analysis, lead to the heightened optical absorption in the visible-near-infrared range. Consequently, flexible nanocomposites of Cu-HTCC/PDMS and Cu-HTCC@PDMS (PDMS = polydimethylsiloxane) are designed as 2 and 3D structures, respectively, that exhibit broad-spectrum solar absorption. These composites promise efficient photo-assisted thermoelectric power generation and water evaporation, demonstrating commendable mechanical stability and flexibility. Notably, the Cu-HTCC@PDMS composite sponge simultaneously exhibits commendable efficiency in both water evaporation (1.47 kg m-2 h-1) and power generation (32.1 mV) under 1 sunlight illumination. These findings unveil new possibilities for innovative photothermal functional materials in diverse solar-driven applications.

Synthesis of borocarbonitride nanosheets from biomass for enhanced charge separation and hydrogen production

Borocarbonitride (BCN) materials have shown significant potential as photocatalysts for hydrogen production. However, traditional bulk BCN exhibits only moderate photocatalytic activity. In this study, we introduce an environmentally conscious and sustainable strategy utilizing biomass-derived carbon sources to synthesize BCN nanosheets. The hydrogen evolution efficiency of BCN-A nanosheets (110 μmol h-1 g-1) exceeds that of bulk BCN photocatalysts (12 μmol h-1 g-1) by 9.1 times, mainly due to the increased surface area (205 m2g-1) and the presence of numerous active sites with enhanced charge separation capabilities. Notably, the biomass-derived BCN nanosheets offer key advantages such as sustainability, cost-effectiveness, and reduced carbon footprint during hydrogen production. These findings highlight the potential of biomass-based BCN nanomaterials to facilitate a greener and more efficient route to hydrogen energy, contributing to the global transition towards renewable energy solutions.

The reconstitution of reed cellulose by the hydrothermal carbonization and acid etching to improve the performance of photocatalytic degradation of antibiotics

As an economical and environment-friendly material, hydrothermal carbonation carbon (HTCC) has been widely used in the field of adsorption and catalysis. Previous studies mainly used glucose as raw material to prepare HTCC. Cellulose in biomass can be further hydrolyzed into carbohydrate; however, there are few reports on the direct preparation of HTCC from biomass and the relevant synthesis mechanism is unclear. In this study, HTCC with efficient photocatalytic performance was prepared from reed straw using dilute acid etching under hydrothermal conditions and was used for the degradation of tetracycline (TC). The mechanism of photodegradation of TC by HTCC was systematically elucidated through various characterization techniques and density functional theory (DFT) calculations. This study provides a new perspective on the preparation of green photocatalysts and demonstrates their promising application in environmental remediation.

Promoting Photocatalytic Carbon Dioxide Reduction by Tuning the Properties of Cocatalysts

Suppressing the amount of carbon dioxide in the atmosphere is an essential measure toward addressing global warming. Specifically, the photocatalytic CO2 reduction reaction (CRR) is an effective strategy because it affords the conversion of CO2 into useful carbon feedstocks by using sunlight and water. However, the practical application of photocatalyst-promoting CRR (CRR photocatalysts) requires significant improvement of their conversion efficiency. Accordingly, extensive research is being conducted toward improving semiconductor photocatalysts, as well as cocatalysts that are loaded as active sites on the photocatalysts. In this review, we summarize recent research and development trends in the improvement of cocatalysts, which have a significant impact on the catalytic activity and selectivity of photocatalytic CRR. We expect that the advanced knowledge provided on the improvement of cocatalysts for CRR in this review will serve as a general guideline to accelerate the development of highly efficient CRR photocatalysts.

Optimization of Fe/Ni organic frameworks with core-shell structures for efficient visible-light-driven reduction of carbon dioxide to carbon monoxide

To address CO₂ emissions caused by the overuse of fossil fuels, photocatalytic CO₂ reduction from metal-organic frameworks (MOFs) to valuable chemicals is critical for energy conversion and storage. Core-shell MOFs improve interfacial interactions, increasing the number of active sites in the catalyst, thereby improving the photocatalytic reduction. In this work, the catalytic performance of Fe/Ni-MOFs toward photocatalytic CO₂ reduction was improved using a bimetallic strategy. We successfully synthesized a series of Fe/Ni-MOFs with a core-shell structure using a single-step approach combined with hydrothermal synthesis. By altering the synthesis conditions of the bimetallic organic skeleton and contrasting it with a single MOF, we successfully synthesized Fe/Ni-T120 through an efficient photocatalytic reduction of CO₂. The results of photocatalytic CO₂ reduction experiments indicated that upon using [Ru(bpy)₃]Cl₂·6H₂O as a photosensitizer and triethanolamine (TEOA) and acetonitrile (MeCN) as sacrificial agents, the CO evolution rate of Fe/Ni-T120 reached 9.74 mmol g^-1 h^-1 and the CO₂ to CO selectivity reached up to 92.1%. Additionally, Fe/Ni-T120 has a broad response range to visible light, a high photocurrent intensity, good chemical stability, and strong photocatalytic efficiency, even after repeated cycles. This study proposes a straightforward method for producing adaptable and stable MOFs for effective photocatalytic CO₂ reduction that is driven by visible light.

Alloying strategies for tuning product selectivity during electrochemical CO2 reduction over Cu

Excessive reliance on fossil fuels has led to the release and accumulation of large quantities of CO₂ into the atmosphere which has raised serious concerns related to environmental pollution and global warming. One way to mitigate this problem is to electrochemically recycle CO₂ to value-added chemicals or fuels using electricity from renewable energy sources. Cu is the only metallic electrocatalyst that has been shown to produce a wide range of industrially important chemicals at appreciable rates. However, low product selectivity is a fundamental issue limiting commercial applications of electrochemical CO₂ reduction over Cu catalysts. Combining copper with other metals that actively contribute to the electrochemical CO₂ reduction reaction process can selectively facilitate generation of desirable products. Alloying Cu can alter surface binding strength through electronic and geometric effects, enhancing the availability of surface confined carbon species, and stabilising key reduction intermediates. As a result, significant research has been undertaken to design and fabricate copper-based alloy catalysts with structures that can enhance the selectivity of targeted products. In this article, progress with use of alloying strategies for development of Cu-alloy catalysts are reviewed. Challenges in achieving high selectivity and possible future directions for development of new copper-based alloy catalysts are considered.

Aerosol processing technique for the synthesis of mixed-phase copper on carbon catalyst: insights into CO2adsorption and photocatalytic activity

In this study, spray pyrolysis; an aerosol processing technique was utilized to produce a mixed-phase copper on carbon (Cu/Cu_xO@C) catalyst. The catalyst production was performed via chemical reduction of copper nitrate by a reducing sugar, i.e. glucose, using aqueous solution. The physical and chemical properties of the produced particles was assessed using various characterization techniques. The synthesis temperature had pronounced effect on the final particles. Since CO₂adsorption onto the catalyst is an important step in catalytic CO₂reduction processes, it was studied using thermogravimetric and temperature programmed desorption techniques. Additionally, photocatalytic activity of the particles was evaluated by gas-phase oxidation of acetylene gas which revealed excellent activity under both UV and visible light irradiation indicating the possible use of wider range of the solar spectrum.

Nitrogen-doped hydrochars from shrimp waste as visible-light photocatalysts: Roles of nitrogen species

The increasing shrimp waste production has caused severe environmental problems. In this study, nitrogen-doped hydrochars (NDHCs) were facilely synthesized from shrimp waste and glucose by one-pot hydrothermal carbonization (HTC). The characterizations showed that NDHCs had large surface areas of up to 30.5 m² g^-1 with numerous functional groups on their porous surfaces. The nitrogen content (1.3-2.8%) and species distribution in NDHCs were associated with the amount of added glucose. These NDHCs were applied as visible-light-induced photocatalysts, and their photocatalytic performances were evaluated by methylene blue (MB) degradation. The removal rate of MB reached 88.9% after 1 h of visible light radiation by NDHC-1, which was 2.3 times higher than that of glucose-derived hydrochar (GHC). The mechanism study showed that the improved photoactivity of NDHCs was attributed to the increased adsorption capacity by porous surface and the promoted formation of hydroxyl radicals by synergistic effects of quaternary N and pyrrolic N during photocatalysis. This study offered a green approach to preparing tunable, efficient, and low-cost photocatalyst from waste biomass and insight into the photocatalytic mechanism of hydrochar materials.

A High-Efficiency Hematite Photoanode with Enhanced Bonding Energy Around Fe Atoms

Hematite nanoarrays are important photoanode materials. However, they suffer from serious problems of charge transfer and surface states; in particular, the surface states hinder the increase in photocurrent. A previous strategy to suppress the surface state is the deposition of an Fe-free metal oxide overlayer. Herein, from the viewpoint of atomic bonding energy, it is found that the strength of bonding around Fe atoms in the hematite is the key to suppressing the surface states. By treating the surface of hematite with Se and NaBH₄ , the Fe₂ O₃ transforms to a double-layer nanostructure. In the outer layer, the Fe-O bonding is reinforced and the Fe-Se bonding is even stronger. Therefore, the surface states are inhibited and the increase in the photocurrent density becomes much faster. Besides, the treatment constructs a nanoscale p-n junction to promote the charge transfer. Improvements are achieved in onset potential (0.25 V shift) and in photocurrent density (5.8 times). This work pinpoints the key to suppressing the surface states and preparing a high-efficiency hematite nanoarray, and deepens our understanding of hematite photoanodes.