Beyond the Thermal Equilibrium Limit of Ammonia Synthesis with Dual Temperature Zone Catalyst Powered by Solar Light

Artificial ammonia synthesis (Haber-Bosch process) is a prototypical exothermic reaction of maximum catalytic yield restricted by the unbreakable equilibrium law. This is because bottlenecked N-2 dissociation necessitates high temperature, but high temperature reversely shifts the thermal equilibrium toward NH3 decomposition. To surmount this equilibrium limit, here, we propose a new scenario of dual-temperature-zone catalysis. Powered by sunlight, the apparent temperature of TiO2-xHy/Fe hybrid reaches 495 degrees C but with local temperature difference up to 137 degrees C between the hot zone (Fe) and cooling zone (TiO2-xHy) owing to the plasmonic local heating effect. The hot Fe bearing hot carriers efficiently dissociates N-2, while working-in-tandem TiO2-xHy well accommodates spilled-over N from Fe via successive hydrogenation, prominently mitigating the reverse equilibrium shift and thus delivering record NH3 concentrations of 1,939 (1 atm) and 19,620 ppm (10 atm) at 495 degrees C,1.55 and 1.57 times the theoretical equilibrium limits of 1,249 and 12,459 ppm, respectively.