Projeto Portugal 2030

Sumário

This project focuses on developing stable and high performing materials for an internal reforming PCFC at 200-300°C, Fig.1. The development of novel materials can potentially improve the efficiency of several other energy storage and conversion devices, such as fuel cells, electrolyzers, and batteries, etc.. Thus, the proposed research is not only relevant to this application but also has broad implications for the advancement of sustainable energy technologies. In the national context, the theme of the proposal is of great relevance to the Portuguese scientific community, which sets research goals on reducing energy import dependency below 65% by 2030[13]. However, the project also addresses the EU challenges aligned with the RIS3 [14] and the 2030 Agenda[15]. By electrochemical promotion, the new PCFC device may overcome the slow kinetics of bioethanol reforming in conventional heterogeneous catalysis at low temperatures, which currently has low H2 selectivity (40-50%@300°C)[16]. The proposal investigates if the thermodynamic equilibrium of bioethanol reforming at low temperatures can be shifted using a PCFC to electrochemically extract and subsequently combust the formed H2 across a protonic membrane. Such innovation would increase bioethanol conversion and selectivity to H2, while also producing electrical energy, to create a new bioethanol fuel cell for the transport sector (Fig.1). Towards this goal, several new materials concepts are suggested for key limiting components: 1) ELECTROLYTE: Proton-conducting analogs of the NASICON family (HZPs),e.g., H5Zr(PO4)3, were recently reported to offer high proton conduction at intermediate temperatures (10^-2S/cm@110°C) but low thermal stability[17]. Conversely, different analogs of the same family, HZr2(PO4)3, offer much higher thermal stability (up to ~400°C)[18–20], but lower conductivities. In the current proposal, we aim to study available solid-solutions in the H5Zr(PO4)3-HZr2(PO4)3 and H1+xZr2-xAx(PO4)3 systems, (A=acceptor dopant), to potentially combine the benefits of both phases in the search for suitable new proton conductors in the 200-300°C range. 2) ANODE: Typical nickel metal anodes are unsuitable at these temperatures due to their high activity for C-deposition. In contrast, layered transition carbides (MXenes, e.g., Ti3C2Tx [10], Ti2CTx[21], Mo2C[22], where Tx are functional groups of –O, –OH and –F on the surfaces) have recently been proposed for heterogeneous catalysis with high activity/selectivity for H2 formation and stability in carbonaceous atmospheres[10,22,23]. Hence, in a novel concept, materials based on Mn+1CnTx (M=transition metal, n=1-4, Tx=–O, –OH and –F on the surfaces [10]) will be tested as new anode electrocatalysts for PCFCs, with the potential to operate in the current application of low temperature bioethanol reforming. SPECIFIC OBJECTIVES 1) To fabricate stable and conductive ceramic electrolyte membranes (target proton conductivity 10^-3-10^-2 S/cm@300°C) and high density (=90%)[24]. 2) To develop new anodes for low temperature bioethanol reforming (target polarization resistances <1?cm^-2@300ºC and porosity 20-35%, competing with high-temperate state-of-the art PCFC electrodes[25]). To provide proof of concept of an internal reforming bioethanol PCFC (target power density =400 mW/cm^2@300°C[26] and =75%H2 selectivity @300°C, in line with those normally found only at much higher temperatures (e.g., 700°C[27]).