Review of Graphitic Carbon Nitride and Its Composite Catalysts for Selective Reduction of CO₂

Abstract

Influenced by "artificial photosynthesis", different energy mimetic fuels such as DME, methanol, formic acid, methane, etc. can be prepared by the reduction or hydrogenation of carbon dioxide (CO 2 ), captured from the atmosphere while maintaining different reaction strategies, such as thermal catalysis, electrocatalysis, photocatalysis, and photoelectrocatalysis, and also by means of various enzymatic reactions. Harvesting ubiquitously inherent solar energy and applying the same in photopropagated CO 2 reduction toward the generation of value-added energy feedstock using apposite semiconductor photocatalysts have proven to be a sustainable and greener process completing the carbon cycle. Graphitic carbon nitride (g-C 3 N 4 ) has been recognized as a highly potent photo-as well as electrocatalyst for the CO 2 reduction reaction (CRR), primarily due to its high chemical and thermal stability, low toxicity, costeffectiveness, visible light absorption capacity, and ingeniously tunable synthetic routes as compared to other semiconductor platforms. Nevertheless, a lower specific surface area, lower electrical conductivity, fast recombination of phototriggered excitons, and narrow visible light absorption window hinder the application of this catalytic material for practical photocatalytic utilization. Adapting certain alteration approaches, such as structural modulation, elemental doping, attachment of metal complex motif, functional group modification of g-C 3 N 4 etc., can dramatically reinforce the photocatalytic activity in the direction of efficient CO 2 reduction. The present review explores the various perceptions of synthetic routes as well as individual optimization techniques of g-C 3 N 4 promoting CO 2 photoreduction adopted by the scientific community from the very outset to the latest findings. Predominantly, this review ruminates on the theoretical and experimental framework of practical photochemical CO 2 reduction on g-C 3 N 4 -based hybrid platforms while elucidating the respective material optimization techniques employed to boost selectivity and efficiency along with their merits and demerits. The future scope of improvement and a comparative discussion are concluded in the form of an imminent panorama.

Chemical reactions of graphitic carbon nitride films with glass surfaces and their impact on photocatalytic activity

“…Photocatalysts are the key to creating a sustainable society through utilizing renewable solar energy. Graphitic carbon nitride (g-CN) is a heptazine-based polymer demonstrating a wide range of photocatalytic applications under visible-light irradiation like water photolysis, [1][2][3][4][5][6][7] CO 2 reduction, 8,9 and degradation of organic pollutants. 10,11 For repeated practical use, it is necessary to immobilize g-CN to avoid the need for filtering off and recapturing the photocatalyst.…”

Ultrasonic-assisted synthesis of porous S-doped carbon nitride ribbons for photocatalytic reduction of CO2

“…GCN is bulky and lacks discernible pores ( Fig. 1 a–b), and its substantial agglomeration was primarily driven by heterogeneous heat transfer during condensation polymerization [35] . In contrast, S-doped carbon nitride samples, including SCN and PSCN, formed thin ribbons.…”

“…Further, The e − are exploited to reduce CO 2 to its radical (CO 2 •− ), as shown in Eq. (2) [35] . The water (H 2 O) oxidation arises at VB of the catalyst to produce the energetic protons (H + ) and oxygen (Eq.…”

Graphitic carbon nitride-based nanostructures as emergent catalysts for carbon monoxide (CO) oxidation

“…24,77–80 There are various reviews discussing in detail the preparation methods of g-C 3 N 4 . 21,28,81–83…”