fig4
![Proton exchange membrane fuel cells: application for value-added chemical productions](https://image.oaes.cc/1de5641c-f286-4136-9d8f-d5812f60369f/cs3044.fig.4.jpg)
Figure 4. Three major approaches for the catalyst layer fabrication. This figure is quoted with permission from Zhao et al.[44]. CCM: The catalyst layer loaded on the proton exchange membrane; CCS: the catalyst layer loaded on the gas diffusion layer; CL: catalyst layer; DTM: the catalyst layer loaded on the proton exchange membrane through transfer; GDL: gas diffusion layer; MEA: membrane electrode assembly.