Robust and efficient hydrogen production performance using nitrogen- and phosphorus-doped microalgal carbon-based metal-free carbon composite

Abstract

Carbon-based metal-free catalysts are attracting attention in different applications. However, these metal-free carbon materials do not have sufficient active sites, resulting in low catalytic activity. Therefore, modification of metal-free carbon materials with appropriate approaches is important. The simultaneous doping of different electronegative heteroatoms has a positive effect on catalytic performance due to the synergistic effect caused by the electronic interactions between different atoms compared to mono-doping. In this study, Spirulina platensis, a microalgae species that is easy to culture, was used as the carbon source. First, ammonia (NH3) and phosphoric acid (H3PO4) activation were used to modify the surface of activated carbon obtained from Spirulina platensis by KOH activation (SPAC). Thus, the SPAC surface is enriched with N(SPAC-N) and P atoms whose electronegativity is different from carbon. These modified carbon particles (SPAC-N-P) were used as a metal-free catalyst to increase the H2 production rate from NaBH4 methanolysis. XRD, TEM, TG/DTG, FTIR and XPS analyses were used for the characterization of the obtained catalysts. FTIR and XPS analyses showed successful incorporation of N, P and O atoms. HGR values of 5737, 6104 and 13,052 mL min−1gcat−1 by SPAC, SPAC-N and SPAC-N-P catalysts were obtained, respectively. There is a significant increase in the catalytic performance of the catalysts obtained with both NH3 and H3PO4 activations.