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 language | English |
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Article number | 102013 |
Journal | Cell Reports Physical Science |
Volume | 5 |
Issue number | 6 |
DOIs | |
Publication status | Published - 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