Removal of hydrogen poisoning by electrostatically polar MgO support for low-pressure NH3 synthesis at a high rate over the Ru catalyst by Wu, S, Peng, Y-K, Chen, T-Y, Mo, J, Large, A, McPherson, I, Chou, H-L, Wilkinson, I, Venturini, F, Grinter, D, Escorihuela, PF, Held, G, Tsang, SCE