Nano-alloyed catalysts have emerged as important parts in modern catalysis, providing superior performances over monometallic counterparts on account of synergistic results [1], [2], [3]. Reaching good management over alloy composition is essential because it profoundly influences catalyst properties like digital construction and energetic websites. Nonetheless, reaching constant and uniform composition in nano-alloy catalysts presents vital challenges [4]. The complexity arises from the necessity to obtain a homogeneous distribution of a number of metals on the atomic degree, whereas balancing the completely different properties such because the potential volatility and reactivity between the constituent metals, particularly parts like Ga [5], Zn [6] and In [7].
Amongst these, Zn-based bimetallic catalysts, equivalent to Cu-Zn [8], Pd-Zn [9], Co-Zn [10], and Pt-Zn [11], have been extensively studied for heterogeneous catalysis over the previous many years. Pt-Zn alloys are significantly notable for his or her catalytic efficiency in varied reactions together with selective oxidation [12], methanol steam reforming [13], and alkane dehydrogenation [14], particularly in propane dehydrogenation (PDH) reactions [15], [16]. Zinc, as a promoter, would modify the digital and structural properties of Pt, which lead typically to improved coke resistance and stability throughout PDH response [14], [17], [18]. Moreover, Zn promotes the dispersion of Pt, growing the supply of energetic websites, enhancing the general catalytic exercise and selectivity in direction of propylene [15], [16]. These options would handle key challenges related to standard Pt-based PDH catalysts and make Pt-Zn alloys a promising candidate for industrial purposes.
The volatility of Zn is a crucial consideration in Zn-based bimetallic catalysts. Many elements equivalent to low melting (419.5 °C) and boiling level (907 °C), weak steel bonding (enthalpy of atomization: 130 kJ/mol) and excessive vapor stress (e.g., 1.5 × 103 Pa at 590 °C) make Zn susceptible to gas-phase transformation beneath excessive temperature [19], [20], [21]. Thereby, in bimetallic alloy system, the volatilization of Zn at elevated temperatures poses challenges for sustaining a steady alloy construction [22], [23], [24], [25]. As an illustration, the lack of Zn in Pt-Zn has been noticed after sensible PDH purposes [22], [23], probably altering the alloy composition and catalytic efficiency.
Alternatively, the volatility of zinc has performed a big position in each large-scale industrial processes and micro-scale purposes equivalent to vacuum metallurgical processes [26], [27], [28] and semiconductor manufacturing [29], [30], [31], [32] for many years. Current developments have leveraged the selective deposition of Zn from ZnO onto silanol nests of zeolites and mesoporous silica to craft extremely energetic and selective catalysts for PDH by Zhao et al. [33]. The chemical vapor deposition (CVD) technique was utilized by Almutairi et al. [34] to introduce well-defined Zn species into zeolite, contributing to homogeneously dispersed Zn cations. Constructing on these revolutionary approaches, we explored a brand new utility of zinc volatility. Fairly than introducing Zn from an exterior supply, we leveraged its inherent volatility throughout the alloy to regulate bimetallic catalyst compositions by way of managed thermal therapy.
On this research, we proposed a novel method to optimize the composition of Pt-Zn alloys by leveraging the risky nature of zinc, aiming to boost their efficiency in PDH reactions. Managed hydrogen pretreatment enabled a gradual discount in Zn content material inside Pt-Zn nanoalloys, stabilizing over time. Notably, this compositional adjustment correlated with a progressive enhancement and stabilization of preliminary propylene productiveness. Provided that compositional adjustments could alter microstructure and elemental dispersion, we employed electron microscopy (EM) to realize atomic-scale insights. Whereas earlier research have examined compositional variations in bimetallic catalysts [35], [36], [37], in-depth understanding of compositional evolution throughout pretreatment stays restricted [38], [39]. The mix of in situ EM and spectroscopy is especially essential because it permits direct remark of structural and compositional dynamics in catalysts beneath related working situations [40], [41]. Consequently, our investigation delved into the volatilization conduct of particular person Pt-Zn NPs beneath completely different warmth therapy situations through equivalent location scanning transmission electron microscopy (IL-STEM) experiments utilizing an in situ gasoline cell. These findings present worthwhile insights for the strategic design and optimization of bimetallic catalysts tailor-made for PDH and different catalytic processes.
