Sub-volt conversion of activated biochar and water for H2 production near equilibrium via biochar-assisted water electrolysis

Nishithan C. Kani, Rohit Chauhan, Samuel A. Olusegun, Ishwar Sharan, Anag Katiyar, David W. House, Sang Won Lee, Alena Jairamsingh, Rajan R. Bhawnani, Dongjin Choi, Adam C. Nielander, Thomas F. Jaramillo, Hae Seok Lee, Anil Oroskar, Vimal C. Srivastava, Shishir Sinha, Joseph A. Gauthier, Meenesh R. Singh

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Sluggish water oxidation reactions limit water electrolysis for H2 production, which can be alleviated by the use of carbon-based materials like agricultural wastes as reducing agents. Biochar from such biomass can reduce equilibrium cell potentials at standard conditions from 1.23 V to 0.21 V by avoiding direct water splitting at the anode. However, some challenges hinder biochar oxidation, including poor biochar binding, electrode caking, and surface passivation. We find that enhanced C/O ratio, crystallinity, and negative zeta potential improve biochar oxidation kinetics at moderate temperatures. Smaller particle sizes and better mixing prevent electrode caking, enhancing biochar stability. Here, we report sub-volt biochar-coupled H2 production, often referred to as a biochar-assisted water electrolysis (BAWE), yielding ∼250 mA/gcat H2 current at 100% Faradaic efficiency. Over 1 mA current was observed at a near-equilibrium cell potential of 0.2 V cell potential. Using a single-junction solar cell-powered BAWE, ∼15 mA H2 is generated at 1 Sun, resulting in ∼4.8% solar-to-hydrogen efficiency, equivalent to ∼35% when the energy of H2 relative to H2O (without biochar) is assumed.

Original languageEnglish
Article number102013
JournalCell Reports Physical Science
Volume5
Issue number6
DOIs
Publication statusPublished - 2024 Jun 19

Bibliographical note

Publisher Copyright:
© 2024 The Authors

Keywords

  • biochar
  • biochar oxidation
  • carbon oxidation
  • green H
  • hydrogen evolution reaction
  • water electrolysis

ASJC Scopus subject areas

  • General Chemistry
  • General Materials Science
  • General Engineering
  • General Energy
  • General Physics and Astronomy

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