The proton exchange membrane electrolysis of water (PEMWE) is a critical process for hydrogen generation. However, the limited ability of electrons and protons to permeate the membrane and the inefficient arrangement of the transport structure in the catalyst layer (CL) presents significant obstacles to the widespread adoption of PEMWE.

A group of researchers from China has developed a hybrid proton-electron conductor—PEDOT:F (Poly(3,4-ethylenedioxythiophene):perfluorosulfonic acid)—which has been incorporated into the CL as a catalytic binder. Their aim was to achieve a uniform anode CL structure and establish an effective three-phase interface by creating a proton/electron double conduction channel.

The researchers published their findings in an open-access paper in the KeAi journal Advanced Powder Materials.

The electron/proton pathway was constructed by introducing MPEC (mixed proton-electron conductor) PEDOT:F as the catalyst binder in the catalyst layer, which constructed more efficient triple-phase boundaries compared to PFSA, resulting in improved catalytic activity and electrochemical performance of the electrolyzer. Zhu et al.

The PEDOT:F exhibits strong perfluorosulfonic acid (PFSA) side chain extensibility, enabling the formation of large hydrophilic ion clusters that form proton-electron transport channels within the CL networks, thus contributing to the surface reactant water adsorption. The PEMWE device employing membrane electrode assembly (MEA) prepared by PEDOT:F-2 demonstrates a competitive voltage of 1.713 ​V under a water-splitting current of 2 ​A ​cm⁻² (1.746 ​V at 2A cm⁻² for MEA prepared by Nafion D520), along with exceptional long-term stability.

Meanwhile, the MEA prepared by PEDOT:F-2 also exhibits lower ohmic resistance, which is reduced by 23.4 ​% and 17.6 ​% at 0.1 ​A ​cm⁻² and 1.5 ​A ​cm⁻², respectively, as compared to the MEA prepared by D520. The augmentation can be ascribed to the superior proton and electron conductivity inherent in PEDOT:F, coupled with its remarkable structural stability. This characteristic enables expeditious mass transfer during electrolytic reactions, thereby enhancing the performance of PEMWE devices.

—Zhu et al.

Compared to the commercial Nafion perfluorosulfonic acid (PFSA), the PEDOT:F ionomers exhibit superior oxygen evolution reaction (OER) performance as catalyst binders. According to senior and co-corresponding author Haolin Tang, both experimental data and Density Functional Theory (DFT) findings validate that the utilization of PEDOT enhances catalytic activity by increasing conductivity and reducing the energy barrier.

Furthermore, the enhanced electronic conductivity of PEDOT:F, combined with its larger hydrophilic ion clusters, eases the adsorption of reactant water on the catalyst’s surface, promoting the electrochemical reaction. Moreover, the electrode containing PEDOT:F displayed outstanding ohmic resistance compared to that made with Nafion, with reductions of 23.4% and 17.6% at current densities of 0.1 A·cm^-2 and 1.5 A·cm^-2, respectively.

Resources

• Liyan Zhu, Hao Zhang, Aojie Zhang, Tian Tian, Yuhan Shen, Mingjuan Wu, Neng Li, Haolin Tang, Enhancing proton exchange membrane water electrolysis Volume 3, Issue 4, 2024, doi: 10.1016/j.apmate.2024.100203