This study provides a significant enhancement in CO2 photoconversion efficiency by the functionalization of a reduced graphene oxide/cadmium sulfide composite (rGO/CdS) with amine. The amine-functionalized graphene/CdS composite (AG/CdS) was obtained in two steps. First, graphene oxide (GO) was selectively deposited via electrostatic interaction with CdS nanoparticles modified with 3-aminopropyltriethoxysilane. Subsequently, ethylenediamine (NH2C2H4NH2) was grafted by an N,N′-dicyclohexylcarbodiimide coupling reaction between the amine group of ethylenediamine and the carboxylic group of GO. As a result, a few layers of amine-functionalized graphene wrapped CdS uniformly, forming a large interfacial area. Under visible light, the photocurrent through the AG/CdS significantly increased because of enhanced charge separation in CdS. The CO2 adsorption capacity on AG/CdS was 4 times greater than that on rGO/CdS at 1 bar. These effects resulted in a methane formation rate of 2.84 μmol/(g h) under visible light and CO2 at 1 bar, corresponding to 3.5 times that observed for rGO/CdS. Interestingly, a high methane formation rate (1.62 μmol/(g h)) was observed for AG/CdS under CO2 at low pressure (0.1 bar), corresponding to a value 20 times greater than that observed for the rGO/CdS. Thus, the enhanced performance for photocatalytic reduction of CO2 on the AG/CdS is due to the improved CO2 adsorption related to the amine groups on amine-functionalized graphene, which sustains the strong absorption of visible light and superior charge-transfer properties in comparison with those of graphene.

Cuprous oxide (Cu2O) is one of the most promising materials for photoreduction of CO2 because of its high conduction band and small band gap, which enable the production of high-potential electrons under visible-light irradiation. However, it is difficult to reduce the CO2 using a Cu2O-based photocatalyst due to fast charge recombination and low photostability. In this work, we enhanced the photocatalytic CO2 conversion activity of Cu2O by hybridization of Cu2O NWAs, carbon layers, and BiVO4 nanoparticles. By construction of a Z-scheme charge flow on a 3-D NWA structure, the BiVO4/carbon-coated Cu2O (BVO/C/Cu2O) NWAs show significantly enhanced charge separation and light harvesting property. As a result, CO formation rate of BVO/C/Cu2O was 9.4 and 4.7 times those of Cu2O mesh and Cu2O NWAs, respectively, under visible light irradiation. In addition, the material retained 98% of its initial photocatalytic CO2 conversion performance after five reaction cycles (20 h) because of the protective carbon layer and Z-schematic charge flow. We believe that this work provides a promising photocatalyst system that combines a 3-D NWA structure and a Z-scheme charge flow for efficient and stable CO2 conversion.

Use of Cu and Cu+ is one of the most promising approaches for the production of C2 products by the electrocatalytic CO2 reduction reaction (CO2RR) because it can facilitate CO2 activation and CC dimerization. However, the selective electrosynthesis of C2+ products on Cu0Cu+ interfaces is critically limited due to the low electrocatalytic production of ethanol relative to ethylene. In this study, a novel porous Cu/Cu2O aerogel network is introduced to afford high ethanol productivity by the electrocatalytic CO2RR. The aerogel is synthesized by a simple chemical redox reaction of a precursor and a reducing agent. CO2RR results reveal that the Cu/Cu2O aerogel produces ethanol as the major product, exhibiting a Faradaic efficiency (FEEtOH) of 41.2% and a partial current density (JEtOH) of 32.55 mA cm−2 in an H‐cell reactor. This is the best electrosynthesis performance for ethanol production reported thus far. Electron microscopy and electrochemical analysis results reveal that this dramatic increase in the electrosynthesis performance for ethanol can be attributed to a large number of Cu0Cu+ interfaces and an increase of the local pH in the confined porous aerogel network structure with a high‐surface‐area.

Ruthenium (Ru) is the most widely used metal as an electrocatalyst for nitrogen (N2) reduction reaction (NRR) because of the relatively high N2 adsorption strength for successive reaction. Recently, it has been well reported that the homogeneous Ru‐based metal alloys such as RuRh, RuPt, and RuCo significantly enhance the selectivity and formation rate of ammonia (NH3). However, the metal combinations for NRR have been limited to several miscible combinations of metals with Ru, although various immiscible combinations have immense potential to show high NRR performance. In this study, an immiscible combination of Ru and copper (Cu) is first utilized, and homogeneous alloy nanoparticles (RuCu NPs) are fabricated by the carbothermal shock method. The RuCu homogeneous NP alloys on cellulose/carbon nanotube sponge exhibit the highest selectivity and NH3 formation rate of ≈31% and −73 μmol h−1 cm−2, respectively. These are the highest values of the selectivity and NH3 formation rates among existing Ru‐based alloy metal combinations.

Carbothermal shock can produce a high surface coverage of metal nanoparticles by introducing cellulose.

In this study, reduced graphene oxide (rGO) and graphene oxide nanoribbons (GONRs) are used to fabricate a composite membrane that exhibits ultrafast water permeance (312.8 L m −2 h −1 bar −1 ) and precise molecular separation (molecular weight cutoff: 269 Da), which surpass the upper bound of previously reported polymer and graphene-based nanofiltration membranes. As two-dimensional GONR exhibits a width on the scale of nanometers, its nanochannels can be enlarged without hindering the stacking of rGO. Moreover, abundant oxygen-containing groups on the edge and surface of GONR enhance the electrostatic interactions between the filtered molecules and the membrane nanochannel. By the synergistic effect, rejection and water flux are considerably increased. Owing to the chemically stable nature of rGO, the composite membrane is highly stable in aqueous media (from acidic to alkaline) and is recyclable during repeated filtration tests.

A Z-scheme graphitic carbon nitride (g-C 3 N 4 )/α-Fe 2 O 3 has been incorporated into a three-dimensional porous graphene aerogel. Graphene aerogels are a promising framework in their use for practical photocatalysis by abundant reaction sites, efficient mass transport of reactants and recyclability through their freestanding framework. At the same time, Z-scheme charge transfer among g-C 3 N 4 , α-Fe 2 O 3 , and conductive graphene inhibits the rapid recombination of the photoinduced electrons and holes. Ternary g-C 3 N4/α-Fe 2 O 3 /graphene aerogels (CNFGA) showed significantly enhanced photocatalytic activity which demonstrated 4.75 times greater methylene blue degradation and 17.5 times higher photocurrent density than those of exfoliated g-C 3 N 4 under visible light. In addition, CNFGA exhibited a robust photostability with a simple recovery method while showing only a ca. 2 % decrease in photocatalytic performance after five cycles. These results suggest that this ternary Z-scheme photocatalyst based on a graphene aerogel has potential use in practical photocatalysis for various environmental applications.[a] C.

Highly selective electrocatalytic CO2 reduction for CO production has attracted tremendous attention for achieving the forthcoming goals of carbon neutrality and widespread industrial utilization and recycling of carbon. Among various approaches, the structural control of the catalyst is particularly interesting because of the facile control of CO2 reduction conditions, such as reaction media and reaction pathways. Thus far, a wide range of nanostructured catalysts, including Au needle tips, Au nanowires, and Au wrinkles, have been used for the enhancement of the selectivity of CO production. In this study, an electrocatalyst with a hierarchical nanostructure for the highly selective production of CO is reported. This hierarchical structure is fabricated by the deposition of Au via e-beam evaporation on a dendritic fibrous nanosilica (KCC-1) template, which is a spherical silica particle consisting of uniformly distributed center-radial fibers. The conversion efficiency of this catalyst is strongly affected by the thickness of the Au deposited on the KCC-1 template, and the highest CO selectivity of ∼98% (at −0.5 V vs. RHE) is obtained at an optimum Au thickness of 50 nm. According to the CO2 electrocatalytic reduction results obtained from KCC-1 with dendritic fibers and a conventional spherical particle without the fibers under various electrolyte conditions, such selectivity enhancement of Au on the KCC-1 template is attributed to the increase in the local pH near the hierarchical catalyst surface. This work provides potential promising templates that exhibit a unique nanostructure for efficient electrocatalysis.