Pyrolysis conditions optimization for biochar synthesis as catalyst for water splitting applications by applying Response surface methodology

Introduction

The global annual accumulation of food waste has been increasing in the last years. Thus, biomass-based catalysts have been selected as a solution to reduce this waste and obtain energy by water splitting process. Therefore, pyrolysis conditions have been optimised by Response surface methodology (RSM) to improve the obtain biochar properties and quality, diminishing overpotential and Tafel slope responses to deal with thermodynamic issues from water splitting. Moreover, our catalyst benefits for its simple coating, as the synthesized biochar is deposited into the selected support by drop deposition where the own material acts as adhesive agent, avoiding polymers as Nafion® or Sustainion®.

Methods

1 g of orange peel was pyrolysed in a tubular oven under different conditions, considering the reaction time (30-720 min) and the reaction temperature (300-900 ºC), with a heating rate of 10ºC/min. Thus, software DesignExpert® has been used for RSM, establishing both reaction temperature and time as input factors and overpotential and Tafel slope as response factors.

Results

Our results showed that the optimal pyrolysis conditions obtained by RSM were applying the highest temperature (900ºC) with the lowest treatment time (30 min), attaining the minimise overpotential (374.8 mV at 10 mA/cm²) for water splitting.

Conclusions

This work demonstrates competitive results in terms of overpotential and Tafel slope with the benchmark catalysts for water splitting, opening the importance of synthesis conditions optimization for catalytic properties.

Acknowledgments

This work was supported by Project H₂-ZeroWaste from AXA Research Fund and the project CINTECX-CHALLENGE 2024. Moreover, the researcher Aida M. Díez is grateful to Ramón y Cajal (RYC2023-044934-I) financial support (MICIU).