Hydrogen is widely recognized as a quintessential clean energy carrier with potential applications across diverse fields—particularly as a fuel in fuel cells, which has garnered substantial research attention
[1−4]. However, the storage and transportation of hydrogen remain formidable challenges to its widespread utilization
[5−7]. Compared with other hydrocarbons, CH
3OH exhibits distinct advantages as a hydrogen carrier: it has the highest hydrogen-to-carbon ratio and lacks stable carbon-carbon bonds. These structural attributes enable methanol to undergo steam reforming under relatively mild temperature conditions, thereby endowing it with significant potential for efficient hydrogen production
[8−10].
Cu-based catalysts have been extensively employed in MSR reactions
[11−15], and their catalytic activity and product selectivity can typically be modulated by incorporating appropriate promoters
[16−19] and optimizing synthesis protocols
[20−24]. Nevertheless, the inherent susceptibility of copper to sintering and deactivation at elevated reaction temperatures—stemming from its intrinsic pyrophoricity—severely constrains its long-term stability
[25−26]. In contrast, Group VIII transition metal catalysts have been developed for their exceptional thermal stability. Specifically, Pd-based catalysts exhibit catalytic activity comparable to that of Cu-based systems at high temperatures
[27−29] while maintaining performance stability over prolonged reaction periods. A critical limitation of such catalysts, however, is their propensity to generate CO, which can induce severe poisoning of fuel cell electrodes. Notably, Iwasa et al.
[30−31] demonstrated that loading Pd onto a ZnO support enhances MSR activity and selectivity toward CO
2. Experimental characterizations revealed that Pd particles alloy with Zn as temperature increases, forming a stable PdZn phase over a broad temperature range. Analogously, Pd/ZnO catalysts also exhibit low CO selectivity in MSR, a behavior attributed to the formation of PdZn alloys. Wang et al.
[32] further reported that PdZn alloy formation significantly improves CO
2 selectivity and overall catalytic activity, with the active phase remaining stable even at 400 °C. By contrast, catalysts that fail to form such alloy structures with ZnO (e.g., Ni, Ru, Co, Ir) typically exhibit poor methanol conversion efficiency and produce substantially higher CO concentrations, limiting their practical applicability
[33].
By integrating the advantages of Cu and Pd-based catalysts, Azenha et al.
[34] rationally designed and synthesized a high-performance PdCu bimetallic catalyst for low-temperature MSR. Compared with monometallic Pd catalysts, the PdCu catalyst displayed 1.5–2 times higher activity and significantly reduced CO formation. Additionally, its long-term stability was enhanced relative to monometallic Cu, with no detectable deactivation observed after 80 h of continuous operation at 240 °C. Complementarily, experimental studies by Mierczynski
[35] and Zhang et al.
[36] confirmed that the PdCu alloy phase markedly boosts H
2 yield during MSR. This alloy adopts a stable face-centered cubic (fcc) structure, with the exposed (111) facet serving as the primary active surface. The latter report
[36] further validated,
via rigorous characterizations including XRD, HAADF-STEM, EDS, XAFS and XPS, that the 1∶1 stoichiometric PdCu alloy exhibits excellent catalytic activity under realistic reaction conditions. These experimental findings provide a robust structural basis for the development of our computational models.
From a theoretical perspective, comprehensive reaction mechanisms for MSR on various pure metal surfaces, including Cu(111)
[37−38], Cu(110)
[39], Cu(211)
[38], Pd(111)
[37], Pt(111)
[40], Co(0001)
[41] and Ni(111)
[42] have been well-established, elucidating their respective reaction pathways and product selectivities. For alloy catalysts, systematic mechanistic investigations have also been reported for systems such as PdZn(111)
[43], PtZn(111)
[44], NiZn(111)
[44] and NiCu(111)
[45]. Given that Pt and Pd belong to the same group in the periodic table and share similar electronic configurations, we employed DFT calculations to systematically investigate MSR reaction pathways on PdCu(111) and PtCu(111) alloy surfaces. By probing the structure-performance relationship of these catalysts, this study advances our understanding of how alloy composition modulates catalytic behavior.