4. Conclusion
(1) The cheap carbon black and graphite mixed with common PTFE and
pore-forming agent are used to construct binary phase region and
hierarchical pore structure at mesoscopic scale, forming an efficient
gas transmission and dispersion network system, which greatly increases
the electrochemical surface area of the catalyst. This simple interface
engineering strategy can also be used as a reference for other reaction
systems requiring gas-solid-liquid three-phase interfaces.
(2) A gas diffusion electrode with reaction layer and diffusion layer is
developed. Gas enters from one side and escapes from the other. A
triphase-interfacial 2e- ORR system over a carbon + PTFE catalyst
enables the reactant O2 to reach the reaction interface
directly from the ambient atmosphere, which simultaneously enhances the
reaction rate and suppresses the competitive hydrogen evolution. Under
the designed 20ml H-type reaction device and optimized conditions, the
generation rate of H2O2 reaches
2.50mmol•cm-2•h-1, and the Faraday
efficiency is 79%, and the cumulative
H2O2 concentration reaches 11.8wt%.
(3) Based on the model of thin plate electrode, the polarization curve
equation is derived and established. Simulation finds that the actual
device polarization processes involve electrochemical polarization and
liquid resistance ohm polarization occurred in the reaction layer, and
ohmic polarization of resistance of bulk phase electrolyte. The
effective reaction depth of electrode decreases rapidly with the
increase of overpotential. Therefore, it is of great significance to pay
more attention to the improvement of catalyst activity. The simulation
also shows that with the increase of current density, the energy
consumed by ohmic polarization of bulk phase electrolyte increases
greatly, which is a problem to be paid attention to in engineering. The
simulation and theoretical analysis of the performance of the pair of
electrodes are also useful for the engineering research and improvement
of other gas diffusion electrodes.
Supported by the National Natural Science Foundation of China (Grant No.
21376226).