Structure-sensitive electrocatalytic reduction of co2 to methanol over carbon-supported intermetallic ptzn nano-alloys

Abstract

The electrochemical reduction of CO<inf>2</inf> (CO<inf>2</inf>RR) to produce valuable synthetic fuel like CH<inf>3</inf>OH 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, CO<inf>2</inf>RR to yield CH<inf>3</inf>OH suffers because of large overpotential, competitive H<inf>2</inf> 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 CO<inf>2</inf>RR. Here, we report for the first time the CO<inf>2</inf>RR over carbon-supported PtZn nano-alloys and probed the crucial role of structures and interfaces as active sites. PtZn/C, Pt<inf>3</inf>Zn/C, and Pt<inf>x</inf>Zn/C (1 < x < 3) synthesized from the metal-organic framework material were characterized structurally and morphologically. The catalysts demonstrated structure dependency toward CH<inf>3</inf>OH selectivity, as the mixed-phase Pt<inf>x</inf>Zn/C outperformed the phase-pure PtZn/C and Pt<inf>3</inf>Zn/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, Pt<inf>x</inf>Zn could not only have facilitated the single electron transfer to adsorbed CO<inf>2</inf> but also showed better binding of the intermediate CO<inf>2</inf> •- over its surface. Moreover, the lower bond energy between the mixed-phase surface and -OCH<inf>3</inf> compared to the phase-pure catalysts has enabled higher CH<inf>3</inf>OH selectivity over Pt<inf>x</inf>Zn. This work opens a wide possibility of studying the role of interfaces between phase-pure nano-alloys toward CO<inf>2</inf>RR. © 2020 American Chemical Society