A 'co-templating' strategy supported by molecular modelling has been used to prepare, for the first time, silicoaluminophosphates with the SAV and KFI framework topologies, each of which has a three-dimensionally connected pore system with high specific volume.
Molecular modeling has been used to assist in the design of a new structure directing agent (SDA) for the synthesis of the AlPO 4 form of STA-2, bis-diazabicyclooctane-butane (BDAB). This is incorporated as a divalent cation within the large cages of STA-2, as determined via a combination of solid-state 13 C and 15 N MAS NMR, supported by 14 N and 1 H-15 N HMQC solution NMR and density functional calculations. Asprepared AlPO 4 STA-2 containing cationic SDA molecules achieves neutrality by the inclusion of hydroxide ions bridging between 5-fold coordinated framework Al atoms. Synchrotron X-ray powder diffraction data of the dehydrated as-prepared form indicates triclinic symmetry (Al 12 P 12 O 48 (OH) 2 • BDAB, P1, a ) 12.3821(2) Å, b ) 12.3795(2) Å, c ) 12.3797(3) Å, R ) 63.3585(8)°, β ) 63.4830(7)°, γ ) 63.4218(7)°) with the distortion from rhombohedral R3 j symmetry resulting from the partial order of hydroxide ions in bridging Al-OH-Al sites within cancrinite cages. Upon calcination in oxygen, the organic SDA is removed, leaving AlPO 4 STA-2 with a pore volume of 0.22 cm 3 g -1 (R3 j , Al 36 P 36 O 144 , a ) 12.9270(2) Å, c ) 30.7976(4) Å). Dehydrated calcined AlPO 4 STA-2 has two crystallographically distinct P and Al sites: 31 P MAS NMR resolves the two distinct P sites, and although 27 Al MAS NMR only partially resolves the two Al sites, they are separated by MQMAS. Furthermore, 2D 27 Al f 31 P MQ-J-HETCOR correlation spectroscopy confirms that each framework Al is linked to the two different P sites via Al-O-P connections in a 3:1 ratio (and vice versa for P linked to different Al). The 27 Al and 31 P resonances are assigned to the crystallographic Al and P sites by calculation of the NMR parameters using the CASTEP DFT program for an energy-minimized AlPO 4 (SAT) framework.
International audienceThe electrocatalytic reduction of carbon dioxide to formic acid on metallic electrodes is known to suffer from low current density and rapid surface contamination by electrolyte impurities. Gas diffusion electrodes (GDE) can overcome these problems due to their high specific surface area. In this work, we show a simple method to prepare indium coated gas diffusion electrodes (GDE-In/C) and their physical and electrochemical characterization. Indium is chosen for its ability to reduce CO 2 to formic acid at relatively low overpotential compared to other metals. The catalytic performance of the GDE-In/C is compared to an indium foil using identical operating conditions. During electrolysis in homogeneous aqueous media (dissolved CO 2) at-1.65 V vs. Ag/AgCl, the partial current density toward HCOOH on the GDE-In/C is 7 times higher than on the indium foil with a faradaic efficiency of 45%. The production of formic acid increases by 15% when a continuous flux of CO 2 gas is applied through the GDE-In/C. In addition, the GDE-In/C shows a good resistance to electrolyte impurities and allows to achieve higher current densities. These promising results are a key milestone in the development of a zero gap cell for gas phase CO 2 electroreductio
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