Hydrochar from Pine Needles as a Green Alternative for Catalytic Electrodes in Energy Applications
Assunta Marrocchi,
Elisa Cerza,
Suhas Chandrasekaran,
Emanuela Sgreccia,
Saulius Kaciulis,
Luigi Vaccaro,
Suanto Syahputra,
Florence Vacandio,
Philippe Knauth,
Maria Luisa Di Vona
Affiliations
Assunta Marrocchi
Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
Elisa Cerza
Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
Suhas Chandrasekaran
Tor Vergata University of Rome, Department Industrial Engineering and International Laboratory: Ionomer Materials for Energy (LIME), 00133 Roma, Italy
Emanuela Sgreccia
Tor Vergata University of Rome, Department Industrial Engineering and International Laboratory: Ionomer Materials for Energy (LIME), 00133 Roma, Italy
Saulius Kaciulis
Institute for the Study of Nanostructured Materials, ISMN-CNR, Monterotondo Stazione, 00015 Roma, Italy
Luigi Vaccaro
Department of Chemistry, Biology and Biotechnology, University of Perugia, Via Elce di Sotto 8, 06123 Perugia, Italy
Suanto Syahputra
Aix Marseille University, CNRS, MADIREL (UMR 7246) and International Laboratory: Ionomer Materials for Energy (LIME), Campus St Jérôme, 13013 Marseille, France
Florence Vacandio
Aix Marseille University, CNRS, MADIREL (UMR 7246) and International Laboratory: Ionomer Materials for Energy (LIME), Campus St Jérôme, 13013 Marseille, France
Philippe Knauth
Aix Marseille University, CNRS, MADIREL (UMR 7246) and International Laboratory: Ionomer Materials for Energy (LIME), Campus St Jérôme, 13013 Marseille, France
Maria Luisa Di Vona
Tor Vergata University of Rome, Department Industrial Engineering and International Laboratory: Ionomer Materials for Energy (LIME), 00133 Roma, Italy
Hydrothermal carbonization (HTC) serves as a sustainable method to transform pine needle waste into nitrogen-doped (N-doped) hydrochars. The primary focus is on evaluating these hydrochars as catalytic electrodes for the oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO2RR), which are pivotal processes with significant environmental implications. Hydrochars were synthesized by varying the parameters such as nitrogen loading, temperature, and residence time. These materials were then thoroughly characterized using diverse analytical techniques, including elemental analysis, density measurements, BET surface area analysis, and spectroscopies like Raman, FTIR, and XPS, along with optical and scanning electron microscopies. The subsequent electrochemical assessment involved preparing electrocatalytic inks by combining hydrochars with an anion exchange ionomer (AEI) to leverage their synergistic effects. To the best of our knowledge, there are no previous reports on catalytic electrodes that simultaneously incorporate both a hydrochar and AEI. Evaluation metrics such as current densities, onset and half-wave potentials, and Koutecky–Levich and Tafel plots provided insights into their electrocatalytic performances. Notably, hydrochars synthesized at 230 °C exhibited an onset potential of 0.92 V vs. RHE, marking the highest reported value for a hydrochar. They also facilitated the exchange of four electrons at 0.26 V vs. RHE in the ORR. Additionally, the CO2RR yielded valuable C2 products like acetaldehyde and acetate. These findings highlight the remarkable electrocatalytic activity of the optimized hydrochars, which could be attributed, at least in part, to their optimal porosity.
