Jean-Félix BOUE
defended his PhD thesis on 20 December 2023
Nanostructured electrodes for H2 production
in front of the jury composed of:
– Vanessa COULET, DR CNRS, MADIREL, Univ. Aix Marseille – Rapporteure
– Têko NAPPORN, DR CNRS, IC2MP, Univ. Poitiers – Rapporteur
– Corinne LAGROST, DR CNRS, ISCR Univ. Rennes – Examinatrice
– Julien CAMBEDOUZOU, Pr, IEM, Univ. Montpellier – Directeur de thèse
– Christophe LAURENT, Pr, CIRIMAT, Univ. Toulouse III – Co-directeur de thèse
– Yaovi HOLADE, MCF HDR, IEM, Univ. Montpellier – Co-encadrant de thèse, invité
– David MESGUICH, MCF, CIRIMAT, Univ. Toulouse III – Invité
Abstract:
Hydrogen is regarded as a highly promising energy resource across various sectors and applications due to its capacity to generate electricity through a reaction with oxygen, producing only water as a byproduct. In this context, water electrolysis remains the preferred method over other approaches that rely on fossil sources, such as methane reforming. However, this method necessitates high-performance electrodes to reduce the energy costs associated with hydrogen production, while avoiding the use of precious metals, which are both scarce and linked to geopolitical issues.
These research efforts have led to the development of porous 3D nanostructured electrodes that combine NiCu nanoparticles with carbon nanotubes (CNT) materials. The adopted strategy comprises three key stages:
– design, synthesis and characterization of NiCu nanoparticles
– preparation, consolidation and characterization of NiCu-xCNT electrodes (x = 4 or 8 the number of walls)
– characterization of electrochemical performance.
A mild chemistry synthesis route and a combustion route were employed to obtain a mixture of NiO CuO nanoparticles. These oxides were then mixed with xNTC. Composite powder mixtures were prepared to create electrodes with catalyst (NiCu alloy) contents of 1, 2, 5, 12, 15, and 20 wt%. The distribution of oxides within the xNTC network was examined using SEM in backscattered electron mode. The results show that the mixing protocol is suitable for contents below 5%wt, and for higher contents, agglomerates of 20 µm nanoparticles are observed, leading to efficiency losses in electrochemistry. These results were observed in powders with 8NTC and 4NTC.
These composite powders were then consolidated by SPS, which also helps in reducing the oxides to form a NiCu alloy that acts as a catalyst for the reaction and after the consolidation porous 3D electrodes are obtained.
Specific surface area values range from 121 to 325 m2.g-1 with porous volumes between 0.16 and 0.44 cm3.g-1. The electrodes were subsequently characterized electrochemically. The best electrodes, with high porous volume (0,43 and 0,44 cm3.g-1) and a good catalyst distribution are competitive in terms of performance and catalyst cost compared to the literature and a reference electrode using platinum. Additionally, the durability test conducted by chrono potentiometry at -100 mA.cm-2 for 24-hour lead to an increase of the performances, which is satisfying.
