Effect of alkali on C–H bond scission over Pt/YSZ catalyst during water-gas-shift, steam-assisted formic acid decomposition and methanol steam reforming

In previous work, Na-doping of Pt/YSZ was found to facilitate the low temperature water gas shift reaction (LT-WGS), and the promoting effect was ascribed to an electronic weakening of the C–H bond of the formate species, a proposed intermediate in the catalytic cycle. Formate has also been implicated as an intermediate in steam-assisted formic acid decomposition (SAFAD) and methanol steam reforming (MSR) pathways. In the current contribution, Na-doping was also found to significantly accelerate the SAFAD reaction. The high activity of Pt/YSZ for SAFAD, as well as the promoting effect of Na, are in stark contrast to the view that formates are too stable, precluding them as intermediates for LT-WGS. With MSR, a remarkable promoting effect of Na doping was observed in the selectivity to CO₂ (>90% for Na-doped relative to 22% for undoped at 300 °C); however, at the doping levels used in the current work, the activity was lower for the Na doped catalyst and further optimization is needed to improve MSR conversion.