Intensifying the charge transfer on N–(CxNx+1) catalysts system: A cutting–edge approach for sunlight driven hydrogen production†

Abstract

Energy crises and global warming have become significant challenges for the developing countries, whereas competent authorities and policymakers ignore the urgency of implementing sustainable solutions, despite the serious nature of energy concerns. Additionally, both issues have been ignored rather than paying attention. I strongly believe, these can be resolved by the proper implementation of scientific and advanced technologies. On the other hand, atmosphere is consistently polluted due to extensive use of fossil fuels that are major contributor of global warming. To save the life on earth, green and carbon free atmosphere is necessary. This project has been designed to explore an alternative source in the form of hydrogen that potentially can produce from water (i.e. renewable source). For this purpose, nitrogen doped graphitic carbon nitride N–(C_xN_x+1) catalysts have been synthesized and assessed for hydrogen production. Catalysts have been prepared via melamine precursor, whereas nitrogen doping was achieved by the hydrothermal treatment. Morphology and optical characteristics have been assessed via XRD, FT–IR, Raman, UV–Vis–DRS, PL, TRPL, EIS, SEM and AFM analytical techniques. Purity, chemical compositions and electron transportation were confirmed by EDX, XPS, EIS and EPR studies. Catalytic reactions were performed in photoreactor (Velp–scientific), whereas hydrogen evolution activities were monitored with gas chromatography (GC–TCD Agilent/7890A). Results revealed that N–(C_xN_x+1) is more active catalyst that delivers almost 5 times more hydrogen (i.e. 16.39 mmol g^–1 h^–1) than pristine gC_xN_x+1 (3.25 mmol g^–1 h^–1). Results indicated that nitrogen dopants facilitate extra electrons on pi–conjugated system that make it more nucleophilic to readily react with H⁺ (electrophilic moieties). During the photoreaction, nucleophilic pi–conjugations of N–(C_xN_x+1) shift fermi energy levels to promote electron transfer on the active sites. On the basis of results and catalytic activities it has been concluded that ascribed catalysts have potential to replace the costly and conventional catalysts associated with hydrogen energy technologies.