Structure-Sensitive Electrocatalytic Reduction of CO₂ to Methanol over Carbon-Supported Intermetallic PtZn...

The electrochemical reduction of CO₂ (CO₂RR) to produce valuable synthetic fuel like CH₃OH not only mitigates the accumulated greenhouse gas from the environment but is also a promising direction toward attenuating our continuous reliance on fossil fuels. However, CO₂RR to yield CH₃OH suffers because of large overpotential, competitive H₂ evolution reaction (HER), and poor product selectivity. In this regard, intermetallic alloy catalysts open up a wide possibility of fine-tuning the electronic property and attain appropriate structures that facilitate selective CO₂RR. Here, we report for the first time the CO₂RR over carbon-supported PtZn nano-alloys and probed the crucial role of structures and interfaces as active sites. PtZn/C, Pt₃Zn/C, and PtZn/C (1 < x < 3) synthesized from the metal-organic framework material were characterized structurally and morphologically. The catalysts demonstrated structure dependency toward CH₃OH selectivity, as the mixed-phase PtZn/C outperformed the phase-pure PtZn/C and Pt₃Zn/C. The structure-dependent reaction mechanism and the kinetics were elucidated over the synthesized catalysts with the help of detail experiments and associated density functional theory calculations. Results showed that in spite of low electrochemically active surface area, PtZn could not only have facilitated the single electron transfer to adsorbed CO₂ but also showed better binding of the intermediate CO₂^•- over its surface. Moreover, the lower bond energy between the mixed-phase surface and -OCH₃ compared to the phase-pure catalysts has enabled higher CH₃OH selectivity over PtZn. This work opens a wide possibility of studying the role of interfaces between phase-pure nano-alloys toward CO₂RR.