Nuclear Production of Hydrogen, Fourth Information Exchange ...

HIGH-TEMPERATURE STEAM ELECTROLYSIS FOR HYDROGEN PRODUCTION: FROM MATERIAL DEVELOPMENT TO STACK OPERATION
Nd 2 NiO 4+δ powder was prepared by nitrate-citrate route as described by Courty, et al. (1973).
Stoichiometric amounts of neodymium and nickel oxides were dissolved in diluted nitric acid. After
addition of a large excess of citric acid, the solution was dehydrated and heated until self-combustion
of the precipitate to obtain submicronic precursor particles (Boehm, 2005). The final annealing was
performed at 1 000°C for 12 hours to obtain a single crystalline phase. The particles were then ball milled
to obtain an average grain size (d 0.5 ) of about 0.8 μm. A terpineol-based slurry was prepared from this
powder and this was deposited on the electrolyte by screen printing and then sintered at 1 100°C for
three hours in air (Lalanne, 2008).
Nd 2 NiO 4+δ was manufactured at ICMCB and deposited by screen printing on half electrolyte
supported cells made of Ni-CGO hydrogen electrode and TZ3Y electrolyte, 90 μm thick. The thickness
of the final Nd 2 NiO 4+δ porous layer was about 30 μm (Figure 2).
Figure 2: SEM micrograph of the Ni-CGO/TZ3Y/Nd 2 NiO 4+δ cell after study
Nd 2 NiO 4+δ
TZ3Y
Ni-CGO
Performance of the cells containing Nd 2 NiO 4+δ oxygen electrode was compared to reference cells
made of the same electrolyte (TZ3Y, 90 μm thick) and a Ni-CGO hydrogen electrode but containing a
classical LSM oxygen electrode.
For these characterisations, the inlet gas composition to the hydrogen electrode was composed of
hydrogen (37%), water vapour (35%) and argon (28%), the total flow rate being 10.7 L.h –1 . The inlet gas
to the anode side was air (7 L.h –1 ). Current collectors on both positive and negative electrodes were
gold grids (1 024 meshes.cm –2 ) and platinum grids (3 600 meshes.cm –2 ), with the platinum grid being
directly in contact with the electrodes. This assembly aims to have a good contact with electrodes.
Measurements were performed at 750°C, 800°C and 850°C, from the lowest to the highest temperature.
i--V curves were recorded under galvanostatic control from open circuit cell voltage (OCV) to the
highest polarisation, then back to OCV.
Results analysis
Performances are evaluated using area specific resistance (ASR) calculated at 1.3 V (slope of i-V curve
between 1.25 and 1.35 V), and using the quantity of hydrogen produced at 1.3 V (nominal voltage) and
at 1.5 V (maximum voltage) according to Faraday’s law. The steam utilisation rate is also calculated as
the molar amount of hydrogen produced (according to Faraday’s law and assuming 100% current
efficiency) divided by the molar amount of water in the inlet cathodic gas.
The degradation rate is calculated from the voltage curve versus time and given as a percentage
of voltage loss per time unit.
122 NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010