Enhanced CO2 photocatalytic reduction on alkali-decorated graphitic carbon nitride

In this work, visible-light photocatalytic reduction performance of carbon dioxide (CO) on graphitic carbon nitride (g-CN) was significantly promoted by the decoration of potassium hydroxide (KOH) on g-CN. More importantly, the role of KOH was thoroughly discussed via various characterizations, control experiments and density functional theory (DFT) calculations. It was found that KOH decoration did not result in any significant difference regards to the morphology, elemental states, BET surface area and light adsorption of g-CN except a drastically enhanced CO adsorption capacity. The promotion effect of KOH on g-CN was mainly contributed by the hydroxide ion (OH) functioning as both a hole accepter and a driving force to keep a dynamically stable amount of HCO (probably the major form of CO to be reduced) on the surface of the catalyst. Moreover, the different extents of influence of NaOH and KOH on g-CN were revealed and further explained using computational results. This study supplements current understanding on alkali-promoted photocatalytic processes and provides new insights into the mechanism of CO photocatalytic reduction

Enriching CO2 Activation Sites on Graphitic Carbon Nitride with Simultaneous Introduction of Electron-Transfer Promoters for Superior Photocatalytic CO2-to-Fuel Conversion

Limited CO2 adsorption and inefficient charge transfer of graphitic carbon nitride (g-C3N4) have been the two major obstacles for its application in photocatalytic CO2 reduction. In this work, a new type of carbon nitride photocatalyst (K-incorporated amino-rich carbon nitride, K-AUCN) is designed and prepared by a facile posttreatment of urea-polymerized g-C3N4 (UCN) using KOH as a chemical activation agent. The resultant K-AUCN has not only enriched intrinsic amino groups for superior CO2 adsorption, but also incorporated potassium and carbon defects as electron promoters for efficient photocatalytic reduction of CO2 in the presence of water vapor. Compared to UCN, the photocatalytic CO2 conversion performance on K-AUCN is drastically promoted by five folds with 7.7-time increase in CO2 adsorption. This work not only presents a simple design of low-cost photocatalyst for CO2 reduction with enhanced performance, but shall also inspire more rational design of efficient catalysts for photocatalytic reduction of CO2 and other specific photocatalytic reactions

Coordination of atomic Co–Pt coupling species at carbon defects as active sites for oxygen reduction reaction

Platinum (Pt) is the state-of-the-art catalyst for oxygen reduction reaction (ORR), but its high cost and scarcity limit its large-scale use. However, if the usage of Pt reduces to a sufficiently low level, this critical barrier maybe overcome. Atomi-cally dispersed metal catalysts with high activity and high atom efficiency endow them with the possibility to achieve this goal. Herein, we report a locally distributed atomic Pt-Co nitrogen-carbon based catalyst (denoted as A-CoPt-NC) with high activity and robust durability for ORR (267 times higher than commercial Pt/C in mass activity). The A-CoPt-NC shows a high selectivity for the 4e- pathway in ORR, differing from the reported 2e- pathway characteristic of atomic Pt catalysts. Density functional theory (DFT) calculations suggest that this high activity originates from the synergistic effect of atomic Pt-Co located on a defected C/N graphene surface. The mechanism is thought to arise from asymmetry in the electron distri-bution around the Pt/Co metal centres, as well as the metal atoms coordination with local environments on the carbon sur-face. This coordination results from N8V4 vacancies (where N8 represents the number of nitrogen atoms, V4 indicates the number of vacant carbon atoms) within the carbon shell that enhances the oxygen reduction reaction via the so-called syner-gistic effect