Potassium and Sulfur Dual Sites on Highly Crystalline Carbon Nitride for Photocatalytic Biorefinery and CO₂ Reduction

Abstract

The co-production of high-value-added chemicals and fuels by coupling biomass photooxidation with carbon dioxide (CO2) photoreduction has attracted wide interest. Nevertheless, there still lacks comprehensive studies. Herein, we synthesized a highly crystalline carbon nitride with potassium and sulfur dual sites (K/S@CN-x) by a salt-template-assisted incorporation method. The incorporation of K/S and high crystallinity resulted in the photocatalytic performance by significantly enhancing the visible-light absorption and accelerated photogenerated charge separation/transfer. Thus, in K/S@CN-0.5, the carbon monoxide (CO) evolution rate (16.27 μmol g–1 h–1) and lactic acid yield (78.07%) were 4.80 times and 1.15 times, respectively, those of CN. Furthermore, density functional theory calculations were performed to investigate the role of K and S dual sites in photocatalytic reactions. Our findings provide unique routes for synthesizing highly crystalline photocatalysts with dual sites and demonstrate the feasibility of photocatalytic selective oxidation of biomass coupled with CO2 reduction.

High-Density Ultrafine Au Nanocluster-Doped Co-LDH Nanocages for Enhanced Visible-Light-Driven CO2 Reduction

“…The transfer and separation efficiency of photoinduced charge carriers were further confirmed by the transient photocurrent (Figure b) and electrochemical impedance (Figure c). In general, the higher the photocurrent intensity and the smaller the circle radius of the semicircular Nyquist plot, the higher the charge-separation efficiency. − Obviously, Au/Co-LDH@[Ru­(bpy) 3 ]­Cl 2 (physical mixing of Au/Co-LDH and [Ru­(bpy) 3 ]­Cl 2 ) shows much higher photocurrent intensity and a smaller semicircle in the Nyquist plot than [Ru­(bpy) 3 ]­Cl 2 and Au/Co-LDH, confirming the positive effects of Au/Co-LDH in promoting the transfer and separation of photoinduced electron–hole pairs. Further analysis reveals that Au/Co-LDH possesses a smaller semicircle than Co-LDH (Figure c), indicating that the high-density Au doping increases the conductivity and internal electron transfer of Co-LDH.…”

Boosting charge transfer in Au-decorated B/K co-doped CN nanosheets towards enhanced photocatalytic CO2 reduction

“…B-atom doping into the CN framework improves exciton dissociation and boosts the electron generation, greatly promoting the separation and migration of charge carriers. 72 Furthermore, the introduction of alkali metal ions coordinated in the skeleton of g-C 3 N 4 can shorten the interlayer distances by coordinating with adjacent N atoms. As a result, the light harvest could be improved and the charge transfer will be accelerated within the stacks.…”

“…Based on the above analysis, a proposed mechanism for the photocatalytic CO 2 reduction over Au/BKCN is illustrated in 72 Furthermore, the introduction of alkali metal ions coordinated in the skeleton of g-C 3 N 4 can shorten the interlayer distances by coordinating with adjacent N atoms. As a result, the light harvest could be improved and the charge transfer will be accelerated within the stacks.…”

Heterogeneous photocatalysis for biomass valorization to organic acids

“…61,62 Through the use of inexpensive semiconductors (e.g., g-C 3 N 4 , TiO 2 , and Zn 1−x Cd x S) as photocatalysts, high yields (71.5-99%) of LA could be obtained from different biomass derivatives under mild conditions (e.g., room temperature to 70 °C, 0.4-8 h, and 0.15-2 mol L −1 alkali). [63][64][65][66][67][68][69][70][71][72][73][74][75]…”