백금 및 팔라듐 기반 합금에 대한 포름산의 전기 화학적 산화에 관한 실험 및 전산연구

Abstract

Direct formic acid fuel cell (DFAFC) can be regarded as the clean and green ener-gy source, in which develop high-efficiency and cheap anode catalysts is important. Palladium and platinum are well noted as anode catalyst for promoting electrochemical oxidation of formic acid (FAO) in DFAFC thanks to their good performance. In here, we study the Pt- and Pd-based alloy catalysts for FAO. The PtBi/C and PtBiPd/C electrocatalysts were synthesized via the irreversible ad-sorption of Pd and Bi ions precursors on commercial Pt/C catalysts. XRD and XPS re-vealed the formation of an alloy structure among Pt, Bi, and Pd atoms. The current of direct formic acid oxidation increased ~ 8 and 16 times for the PtBi/C and PtBiPd/C catalysts than commercial Pt/C. In addition, the increased ratio between the current of direct formic acid oxidation and the current of indirect formic acid oxidation for the PtBi/C and PtBiPd/C catalysts suggest that the dehydrogenation pathway is dominant with less CO formation on these catalysts. Furthermore, Pd modified the BiPt/C im-prove the potential of Bi leaching to keep catalysts activity. We have found that RuPdPt/C has a best performance with less Ru and a large num-ber of Pd than the PtPd/C and Pt/C by experiments results with the density functional theory (DFT), in which RuPdPt/C not only improve the direct formic acid oxidation, but also increase current of indirect formic acid oxidation by the OH of water dissocia-tion as the oxidizing agent. Furthermore, using combined approach of DFT calculations and microkinetic mod-elling (MK), we investigated the fundamental aspects of FAO catalysed by bimetallic M@Pd(111) single-atom surface alloys (where M = Fe, Cu, Zn, Ru, Co, Mo). Our re-sults suggest that M@Pd(111) are highly stable and outperforms Pd(111) for FAO via primarily the direct mechanism: HCOOH → *HCOO (formate) → CO2 + 2H+ + 2e-. It is revealed that the decoordination of *HCOO from bidentate to monodentate adsorption mode (i.e., *bHuCOO → *mHdCOO) followed via the facile carbonyl-H abstraction forming CO2 + (H++e-) could be the potential-determining steps. Moreover, Mo@Pd(111) is predicted to be the most promising bimetallic Pd-based catalyst for FAO based on the weakest *CO binding and the strongest *OH binding with alloyed Mo, which therefore can be used as an effective descriptor for designing FAO catalysts with high activity. For studying the effects of ensemble Mo on the Pd(111) surface, We added the ex-plicit solvation model is closer to the real condition of FAO. Monomers, dimers, trimers, and tetramers are selected as typical Mo ensembles. Meanwhile, interval and adjacent Mo atom have been investigated, we have verified that interval Mo atoms decorated have a better performance than adjacent structures. Mo1Pd is the best profit catalyst for FAO as a direct reaction by intermediates *HCOO, bHuCOO→*mHdCOO as potential-determining step (PDS). Meanwhile, the binding strength of OH can be a descriptor to redefect the barrier of PDS, Mo1Pd is a potential catalyst due to the moderate binding energy of OH. In this work, Pt-based and Pd-based tri-metallic and di-metallic metal even single atom catalysts were studied by experiment and DFT calculation, we found that Pt or Pd can be modified by other metal can get higher performance for FAO due to the elec-tronic, geometric, and third body effects, PtBiPd/C and RuPdPt/C the promising tri-metallic catalysts and the single atom catalyst have valuable catalytic activity, Mo, Ru, Fe, Co, Ni can be combined with Pd as he potential catalyst for FAO.