Cu/PCN Metal-Semiconductor Heterojunction by Thermal Reduction for Photoreaction of CO₂-Aerated H₂O to CH₃OH and C₂H₅OH

Abstract

g-C 3 N 4 -based materials show potential for photoreduction of CO 2 to oxygenates but are subjected to fast recombination of photogenerated charge carriers. Here, a novel Cu-dispersive protonated g-C 3 N 4 (PCN) metal-semiconductor (m-s) heterojunction from thermal reduction of a Cu 2 O/PCN precursor was prepared and characterized using in situ X-ray diffraction, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible (UV–vis) spectra, photoluminescence (PL) spectra, transient photocurrent response, and electrochemical impedance spectroscopy (EIS). The Cu amount in Cu/PCN and the reduction temperature affected the generation of CH 3 OH and C 2 H 5 OH from the photoreaction of CO 2 -aerated H 2 O. During calcination of Cu 2 O/PCN in N 2 at 550 °C, Cu 2 O was completely reduced to Cu with even dispersion, and a m-s heterojunction was obtained. With thermal exfoliation, Cu/PCN showed a specific surface area and layer spacing larger than those of PCN. Cu/PCN-0.5 (12.8 wt % Cu) exhibited a total carbon yield of 25.0 μmol·g –1 under UV–vis irradiation for 4 h, higher than that of Cu 2 O/PCN (13.6 μmol·g –1 ) and PCN (6.0 μmol·g –1 ). The selectivity for CH 3 OH and C 2 H 5 OH was 51.42 and 46.14%, respectively. The PL spectra, transient photocurrent response, and EIS characterizations indicated that Cu/PCN heterojunction promotes the separation of electrons and holes and suppresses their recombination. The calculated conduction band position was more negative, which is conducive to the multielectron reactions for CH 3 OH and C 2 H 5 OH generation.

Size Effect of Cu Nanoparticles in Cu/g-C3N4 Composites on Properties for Highly Efficient Photocatalytic Reduction of CO2 to Methanol

“…As the results displayed in Figure a–c, the optimal concentration of Cu precursor solution is 5.1 mmol/L. Increasing the concentration of Cu precursor solution will increase the surface concentration of Cu active sites in the synthesized composites; however, a too high concentration of Cu precursor would lead to the aggregation of active components covering the active sites, in turn decreasing its catalytic performance . The results of temperature evaluation (Figure b) indicated that MeOH yield reached its highest value of 675 μmol·g –1 ·h –1 at 20 °C, which may be ascribed to the fact that low temperature is disadvantageous to the desorption of intermediates and/or products, while high temperature reduces the solubility of CO 2 in water and inhibits the adsorption of CO 2 on the catalyst surface .…”

“…Increasing the concentration of Cu precursor solution will increase the surface concentration of Cu active sites in the synthesized composites; 70 however, a too high concentration of Cu precursor would lead to the aggregation of active components covering the active sites, in turn decreasing its catalytic performance. 71 The results of temperature evaluation (Figure 6b) indicated that MeOH yield reached its highest value of 675 μmol•g −1 •h −1 at 20 °C, which may be ascribed to the fact that low temperature is disadvantageous to the desorption of intermediates and/or products, while high temperature reduces the solubility of CO 2 in water and inhibits the adsorption of CO 2 on the catalyst surface. 72 A similar phenomenon was also found in the investigation of catalyst dosage (Figure 6c), which should be attributed to the lack of available catalytic sites when the catalysts are insufficient, whereas the shading effect of excessive catalysts is also detrimental to the reaction.…”

N‐methyl‐D‐aspartic acid receptor 2A functionalized stationary phase: A reliable method for pursuing potential ligands against Alzheimer's disease from natural products

“…As shown in Figure 2 E, the binding energy peak of 284.9 eV was dominantly attributed to the C atom in surface aliphatic carbon (C‐C). 13 The binding energies of 400.68 and 532.28 eV were mainly attributed to the N and O elements in N‐H 14 and hydroxyl oxygen (C‐O), 15 respectively. The surface content of C atom was 89.03% in bared microspheres, while its content was gradually decreased in ibrutinib‐modified microspheres (84.38%) and NMDA‐2A‐modified microspheres (71.34%).…”

Cu-Based Materials for Enhanced C2+ Product Selectivity in Photo-/Electro-Catalytic CO2 Reduction: Challenges and Prospects

“…For instance, the introduction of Cu (metal, oxide, and quantum dots) as cocatalyst for heterostructures with various semiconductors (such as g-C 3 N 4 , TiO 2 , ZnV 2 O 4 , etc.) was demonstrated to effectively broaden the photoresponse range and effectively improve the PCO 2 RR activity/selectivity toward C 2+ compounds [119][120][121][122][123][124][125][126]. It is worth noting that despite metal copper itself does not have photocatalytic activity, it has high electrical conductivity, which may enhance the effectiveness of other photocatalysts when combined with them.…”