RuOx-PtZn catalyst boosting methanol electro-oxidation by synergic water-activation for high-performance direct methanol fuel cell

doi:10.1016/S1872-2067(25)64836-4

Abstract

Abstract:

For achieving high-power and low-platinum direct methanol fuel cell (DMFC) under proton-exchange-membrane, we introduce the oxidation-state ruthenium species as H₂O-activation centers stabilized on PtZn NPs to boost methanol-oxidation reaction (MOR). The Zn-regulated Ru centers, approaching bivalent states, enhance interfacial H₂O-capture/dissociation and OH-transfer, enabling rapid CO* removal from adjacent Pt sites. It exhibits an outstanding mass activity of MOR at 2.71 A mg_Pt^-1 and powers a DMFC with 191.2 mW cm^-2 peak density (382.4 W g_Pt^-1) while maintaining 125-hour stability, higher than documented results to date, essentially different from traditional alloy catalysts. Combined ab initio molecular dynamics simulations and in-situ spectroscopy reveal a dense O-down water network around Ru centers, where intermediate RuO(OH)₂ structure significantly deceases the H₂O-dissociation barrier. Kinetic isotope effect tests (CH₃OH/H₂O vs. D₂O) show J_H2O/D2O = 4.2 for RuO_x-PtZn/C at 0.85 V_RHE, versus 16.2 for RuO_x-Pt/C, directly confirming superior water activation efficiency of RuO_x-PtZn/C. We envision that the comprehensive understanding of high-performance MOR on RuO_x-PtZn/C through experimental-theoretical approaches will contribute to the practical application of DMFC as early as possible.

Key words: Oxidation-state ruthenium, RuO(OH)₂, H₂O activation, Methanol oxidation reaction, Direct methanol fuel cell

Chenjia Liang, Jun Yao, Ningze Gao, Xiaoxia Hou, Haoyu Lu, Ruiyao Zhao, Ziheng Zhuang, Jie Yang, Liwen Wang, Xiangke Guo, Nianhua Xue, Tao Wang, Yan Zhu, Weiping Ding. RuO_x-PtZn catalyst boosting methanol electro-oxidation by synergic water-activation for high-performance direct methanol fuel cell[J]. Chinese Journal of Catalysis, 2026, 80: 304-315.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(25)64836-4

https://www.cjcatal.com/EN/Y2026/V80/I1/304

Figures/Tables 8

Scheme 1. Schematic diagram to elucidate the preparation of RuOx-PtZn catalyst and its synergic mechanism for MOR with bivalent Ru.

Fig. 1. The Structural Characterization of RuOx-PtZn/C. (A) Schematic diagram of catalytic-deposition process of Ru on PtZn NPs surface. (B) The HR-TEM image of RuOx-PtZn/C. Inset shows the size distribution of RuOx-PtZn NPs. (C) The HADDF-STEM image of RuOx-PtZn NPs. (D) The intensity surface plot of enlarged region in Fig. 1(C). (E) The EDS mapping of RuOx-PtZn NPs, including Pt, Zn, and Ru element and mixing.

Fig. 2. The electronic and coordinated structure of RuOx-PtZn/C. The Ru K-edge XANES and charge-state fitting (A), fitting EXAFS (B) and Wavelet transforms for the k2-weighted Ru K-edge EXAFS signal (C) for RuOx-Pt/C and RuOx-PtZn/C. The XPS Pt 4f (D) and Zn 2p3/2 (E) spectra of PtZn/C and RuOx-PtZn/C (Inset: the schematic diagram of electron transfer between Ru and Zn).

Fig. 3. The MOR evaluation of RuOx-PtZn/C in half cell and DMFC. (A) The CV curves of different catalysts in N2-saturated 0.1 mol L?1 HClO4 and 1.0 mol L?1 MeOH. (B) The mass activity (MA) improvement after Ru deposition on Pt/C and PtZn/C. (C) The overpotential (@10 mA cm?2) and MA of different elements on PtZn surface. (D) The comparison of MOR activity between RuOx-PtZn/C and reported catalysts in a three-electrode system [3,5,7,8,17,19,20,35-39]. (E) The polarization and power curve in DMFC at 90 °C with iR-free (high-purity O2 with 100% RH: 500 sccm; 2.0 mol L?1 MeOH: 2 mL min?1). (F) The comparison of RuOx-PtZn/C and reported catalysts as anodes for DMFC [5-8,17,39-41]. (G) The stability test of RuOx-PtZn/C on the 2×2 cm MEA at 70 °C without iR-correct (high-purity and atmospheric-pressure O2 with 67% RH: 300 mL min?1; 1.0 mol L?1 MeOH: 0.5 mL min?1).

Fig. 4. The surface species evolution on RuOx-PtZn/C during MOR process. (A) Electrochemical in-situ FTIR spectra for PtZn/C, RuOx-Pt/C and RuOx-PtZn/C in N2-saturated 0.1 mol L?1 HClO4 and 1.0 mol L?1 MeOH electrolyte. (B) The peak fitting of O-H stretching vibration at 0.6 V from the electrochemical in-situ FTIR spectra for PtZn/C, RuOx-Pt/C and RuOx-PtZn/C. (C) The KIE test of RuOx-Pt/C and RuOx-PtZn/C in N2-saturated 0.1 mol L?1 HClO4 and 1.0 mol L?1 MeOH electrolyte with H2O or D2O as medium. (D) The m/z = 44 signal in DEMS of RuOx-Pt/C and RuOx-PtZn/C in N2-saturated 0.1 mol L?1 HClO4 and 1.0 mol L?1 MeOH electrolyte. (E) The schematic diagram of enhancing H2O-activation process, including H2O-capture and H2O-dissociation, on RuOx-PtZn/C.

Fig. 5. The properties of multi-layer water around RuOx-PtZn. (A) The interface model between different catalysts and methanol aqueous solution. (B) The comparison of H2O molecules, H-bond number, and average H-band bond length within the range of 6 ? above the catalyst surface. (C) The radial distribution function of Ru-O (O atom in H2O) for RuOx-Pt and RuOx-PtZn. (D) The statistics of z-axis distribution of H2O molecules on different catalyst surfaces.

Fig. 6. Full elucidation about the MOR mechanism on RuOx-PtZn/C. (A) The various intermediate models during the MOR process on the RuOx-Pt3Zn (111) surface. (B) The Gibbs free energy diagram for H2O# activation and CO* oxidation process. (C) The pCOHP of Ru-O in RuOx-Pt (111) and RuOx-Pt3Zn (111), with H2O# adsorption. (D) The transition state of H2O + # + *→ H* + OH# process.

Table 1 The key process energy barrier and key species adsorption energy.

	H₂O-dissociation barrier (eV)	OH^#-adsorption energy (eV)	CO*-oxidation barrier (eV)
Pt₃Zn	0.860	‒0.791	1.487
RuO_x-Pt	0.492	‒0.699	1.063
RuO_x-Pt₃Zn	0.431	‒0.504	0.686

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