Carbides and nitrides derived from earth-abundant elements are promising catalysts for NH3 decomposition, a key reaction for carbon-free hydrogen production. However, their mechanisms under practical conditions remain insufficiently understood, and reliance on costly Ru catalysts limits broader deployment. Here, we integrate density functional theory, microkinetic modeling, and experimental validation to investigate Co3C and Co3N as cost-effective alternatives. The experimentally relevant Co3C(112) facet exhibits lower activation barrier for NN coupling and achieves TOFs up to two orders of magnitude higher than Co3C(001)-C and Ru(1013) and four to five orders of magnitude higher than Ru(0001) and Co3N(001)-N at 400 °C, closely aligning with the experiments. Degree-of-rate-control analysis further reveals strong surface dependence of the dominant kinetic limitation: NN recombination controls Ru(0001), Co3C(001)-C, and Co3N(001)-N at elevated temperatures, whereas NHx* dehydrogenation governs Co3C(112) and Ru(1013). To validate the computational predictions, Co3C was synthesized and benchmarked against commercial Ru-black. Although Ru-black showed higher NH3 conversion, Co3C exhibited higher surface-area-normalized H2 production rates and 5–10 times higher experimental TOFs than Ru-black at 350–475 °C, supporting its higher inherent activity. Our findings show that Co3C is a promising earth-abundant alternative for NH3 decomposition and demonstrate the importance of integrating multiscale modeling with experimental validation for rational catalyst design.
Direct oxidative polymerization of phenolic pollutants offers a carbon-retentive strategy for reducing oxidant consumption, yet its pathway selectivity remains difficult to regulate. Herein, Cu phthalocyanine (CuPc) was anchored onto carbon nanotubes (CNTs) with different diameters to construct CuPc/CNTs catalysts, integrating nanoconfinement with curvature-strain-induced modulation of Cu−N4 active sites. Small-diameter CuPc/CNT5 exhibited optimal activity and directed oxidation transfer process (DOTP) pathway selectivity, achieving a phenol (PhOH) degradation rate constant of 1.078 min−1 and a polymerization transfer (PT) ratio of 92.07%, which were 4.47 and 2.86 times those of large-diameter CuPc/CNT25, respectively. Mechanistic studies revealed that PhOH removal was dominated by deprotonation-assisted interfacial electron transfer, generating PhO·/PhO+ intermediates for interfacial coupling polymerization. In situ Raman analysis indicated that peroxymonosulfate (PMS) activation generated surface-bound PMS*. COMSOL simulations and theoretical calculations further showed that small-diameter nanochannels increased the local PhO· concentration by 4.7-fold while the curvature-induced upshift of the Cu d-band center and enhanced Cu 3d-N 2p coupling promoted PMS* formation and PhOH to PhO·/PhO+ conversion. Such confinement and electronic coupling ultimately directed PhOH transformation toward the DOTP pathway. These findings provide a strategy for engineering interfacial microenvironments toward selective nonradical oxidation in water treatment.
