Four Cu/SAPO-34 catalysts are used to research the effect of their acid content on their NH₃-SCR activity, by changing the proportion of Si in the catalyst. Though the catalysts exhibit similar Cu loading performed by an ion-exchange method, they lead to different NO conversions in the temperature range of 120–600 °C. The NH₃-TPD results show that varying the proportion of Si can adjust the acid content of SAPO-34. In the low temperature range, kinetic tests prove that the various acid contents did not affect the apparent activation energy (E_a) of the Selective Catalytic Reduction by NH₃ (NH₃-SCR) over Cu/SAPO-34. But it is found that the acid densities are related to the NO conversion at low temperature. In the high temperature range, increasing the acid content of the Cu/SAPO-34 catalysts inhibits the observed NH₃ conversions in the NH₃ oxidation results. As NH₃ oxidation and NH₃-SCR are competing reactions and the former can decrease NO conversion, this inhibition is therefore beneficial to NH₃-SCR. Finally, the influence of the acid content of the catalysts on the NH₃ oxidation is also investigated by kinetic tests.

The process of CH₄ cracking into H₂ and carbon has gained wide attention for hydrogen production. However, traditional catalysis methods suffer rapid deactivation due to severe carbon deposition. In this study, we discover that effective CH₄ cracking can be achieved at 450 °C over a Re/Ni single-atom alloy via ball milling. To explore single-atom alloy catalysis, we construct a library of 10,950 transition metal single-atom alloy surfaces and screen candidates based on C–H dissociation energy barriers predicted by a machine learning model. Experimental validation identifies Ir/Ni and Re/Ni as top performers. Notably, the non-noble metal Re/Ni achieves a hydrogen yield of 10.7 gH₂ gcat^–1 h^–1 with 99.9% selectivity and 7.75% CH₄ conversion at 450 °C, 1 atm. Here, we show the mechanical energy boosts CH₄ conversion clearly and sustained CH₄ cracking over 240 h is achieved, significantly surpassing other approaches in the literature.