ABSTRACT
Critically, the central metal atoms along with their coordination environment play a significant role in the catalytic performance of single-atom catalysts (SACs). Herein, 12 single Fe, Mo, and Ru atoms supported on defective graphene are theoretically deigned for investigation of their structural and electronic properties and catalytic nitrogen reduction reaction (NRR) performance using first-principles calculations. Our results reveal that graphene with vacancies can be an ideal anchoring site for stabilizing isolated metal atoms owing to the strong metal-support interaction, forming stable TMCx or TMNx active centers (x = 3 or 4). Six SACs are screened as promising NRR catalyst candidates with excellent activity and selectivity during NRR, and RuN3 is identified as the optimal one with an overpotential of ≥0.10 V via the distal mechanism.
ABSTRACT
Photocatalytic nitrogen reduction reaction (NRR) is a promising, green route to chemically reducing N2 into NH3 under ambient conditions, correlating to the N2 fixation process of nitrogenase enzymes. To achieve high-yield NRR with sunlight as the driving force, high-performance photocatalysts are essential. One-dimensional silicon nanowires (1D SiNWs) are a great photoelectric candidate, but inactive for NRR due to their inability to capture N2. In this study, we proposed SiNWs doped by p-block elements (B, C, P) to tune the affinity to N2 and demonstrated that two-coordinated boron (B2C) offers an ultra-low overpotential (η) of 0.34 V to catalyze full NRR, which is even much lower than that of flat benchmark Ru(0001) catalysts (η = 0.92 V). Moreover, aspects including suppressed hydrogen evolution reaction (HER), high-spin ground state of the B2C site, and decreased band gap after B-doping ensure the high selectivity and photocatalytic activity. Finally, this work not only shows the potential use of metal-free p-block element-based catalysts, but also would facilitate the development of 1D nanomaterials towards efficient reduction of N2 into NH3.
ABSTRACT
Catalytic antibodies are immunoglobulin proteins that are capable of catalyzing multiple reactions with diverse substrates. Aldolase catalytic antibody 38C2 catalyzes aldol and retro-aldol reactions via an enamine mechanism. Therefore, 38C2 has a high potential to be used in prodrug activation, and it is currently developed for selective chemotherapy. For medical applications, its humanization is essential, and therefore, the understanding of the three-dimensional (3D) spatial atomistic structure of 38C2 is mandatory. In this study, it was attempted to construct the 3D atomic structure of humanized abzyme 38C2 using computational methods. A homology modeled structure was simulated for 100 ns with classical molecular dynamics simulations for its dynamics stability. The accuracy of the constructed model was further evaluated with various theoretical methods. The binding of four selected natural substrates to the constructed structure was studied in detail to further validate the model. Finally, to evaluate the reaction readiness of the constructed protein, the first step of the catalytic reaction has been successfully carried out with QST3/IRC calculations using the DFT/B3LYP-6-31G level of theory in the presence of extracted catalytic residues with the preserved coordinates in implicit water. Hence, the reaction readiness of the proposed protein structure, along with all the other validation tests, strongly proves that the modeled structure has high accuracy. This study, therefore, sheds new light on the structure, mechanism of action and applications of the 38C2 abzyme by constructing and validating its full 3D atomistic model. Further, this highly reliable modeled structure will expedite and facilitate future 38C2-based drug discovery.Communicated by Ramaswamy H. Sarma.
