A need exists to reduce the elevated levels of nitrate (NO3-) in drinking water as it can cause health hazards like blue baby syndrome and thyroid cancer. Current methods of doing so—such as physical separation and chemical degradation—may degrade the catalyst used or even leave the NO3- intact. We have previously demonstrated that nickel phosphide (Ni2P) is a capable catalyst for NO3- hydrogenation, which is a rapid, near-ambient alternate method of NO3- reduction that leaves the catalyst intact. Based on this observation, we select clathrates with nickel phosphide frameworks (ANi2P4 (A = Ba, Sr)) as NO3- hydrogenation catalysts. These bulk clathrates show no catalytic activity at 60 °C and 1 atm H2 without any prior treatment, but after hand-grinding and H2 annealing BaNi2P4 reduces up to 75% NO3- within 12 h. We note that longer grinding times result in higher catalytic activity, likely due to the higher surface area of smaller, ground particles. Additionally, both clathrates still show catalytic activity when H2SO4 is swapped out for HCl or HNO3 as proton sources, and SrNi2P4 outperforms BaNi2P4 with these new acids. Activated ANi2P4 can also catalyze nitroarene reduction, selectively forming condensation products like azoxybenzene early on then reduce to primary amines with more reaction time. The efficacy of these clathrates opens the way to clathrate catalysts with other alkaline-earth guest atoms or clathrate catalysts on the nanoscale.

Can nickel phosphide clathrates be viable catalysts?

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.