“…13,14 Potential chemical modifiers proposed previously were noble metals with high melting points, such as palladium (Pd), platinum, iridium, rhodium, tantalum, titanium, tungsten, lanthanum, arsenic, and ruthenium. 9,[15][16][17][18][19][20][21][22] Furthermore, elements that form carbides such as molybdenum, hafnium, niobium, tungsten, tantalum, and zirconium, as well as NH 4 HPO 4 -Mg(NO 3 ) 2 , nitric acid, and silver nanoparticles have also been suggested. 21,23,24 How exactly the chemical modifier works is a matter of debate.…”