Insights into the effects of pulsed parameters on H2O2 synthesis by two-electron oxygen reduction under pulsed electrocatalysis

Abstract

Pulsed electrocatalysis is emerging as a promising strategy for the improvement of electrocatalytic performance. Herein, the 2-electron oxygen reduction reaction (2eORR) for H2O2 synthesis was taken as a model reaction to explore the effects of pulsed parameters on electrocatalysis. Firstly, the key parameters of a square wave pulse were determined by theoretical analysis and electrochemical testing. Secondly, we found that the pulsed period of the square wave pulse should be neither too short nor too long due to the opposing effects of non-Faradaic and diffusion processes. The lower duty ratio was more favorable for 2eORR. Finally, the effects of the pulsed waveform were explored. We found that the enhanced effects on 2eORR under the rapid sweep potential of a triangular or sine wave were similar to those for a square wave with a short period. Under a sine wave pulse with a frequency of 0.2 Hz, the H2O2 production rate and Faradaic efficiency of 2eORR were increased by 1.4 times and 3.62 times, respectively, compared with the results obtained under constant potential, and the energy consumption was reduced by 75 %. The enhanced effects described above could be attributed to the diffusion layer becoming thinner while the pulsed potential was applied. The reaction rate was increased by the diffusion of reactants (i.e., O2, H+) to the electrode surface and the intrinsic selectivity of 2eORR was increased by the oxygen-rich environment. In addition, the ineffective electroreduction of H2O2 was also reduced by the diffusion of H2O2 toward the bulk solution. This work provides new insights into the determination of parameters, waveform effects and the mechanism of pulsed electrocatalysis.

Keywords

• Pulsed electrocatalysis
• Hydrogen peroxide
• 2-electron oxygen reduction reaction
• Pulsed parameters
• Pulsed waveform