High pressure synthesis of phosphine from the elements and the discovery of the missing (PH3)2H2 tile

Abstract

High pressure reactivity of phosphorus and hydrogen is relevant to fundamental chemistry, energy conversion and storage, and materials science. Here we report the synthesis of (PH3)2H2, a crystalline van der Waals (vdW) compound (I4cm) made of PH3 and H2 molecules, in a Diamond Anvil Cell by direct catalyst-free high pressure (1.2 GPa) and high temperature (T ≲ 1000 K) chemical reaction of black phosphorus and liquid hydrogen, followed by room T compression above 3.5 GPa. Group 15 elements were previously not known to form H2-containing vdW compounds of their molecular hydrides. The observation of (PH3)2H2, identified by synchrotron X-ray diffraction and vibrational spectroscopy (FTIR, Raman), therefore represents the discovery of a previously missing tile, specifically corresponding to P for pnictogens, in the ability of non-metallic elements to form such compounds. Significant chemical implications encompass reactivity of the elements under extreme conditions, with the observation of the P analogue of the Haber-Bosch reaction for N, fundamental bond theory, and predicted high pressure superconductivity in P-H systems.

Single‐Bonded Cubic AsN from High‐Pressure and High‐Temperature Chemical Reactivity of Arsenic and Nitrogen

“…While from a chemical point of view the experimental results of this study mark a significant advancement about reactivity and bond theory in pnictogens, providing insights on the chemical interaction between As and N and once again highlighting the key role played by the electron lone pairs in the high pressure chemistry of pnictogens,[ 21 , 29 , 72 ] the discovery and structural characterization of AsN experimentally confirm the theoretical indications for the existence of novel nitrides,[ 2 , 28 ] and open new perspectives for the design and high pressure synthesis of advanced As and N based inorganic materials of energetic and technological relevance.…”

High-Pressure and High-Temperature Chemistry of Phosphorus and Nitrogen: Synthesis and Characterization of α- and γ-P3N5

“…Within this picture, P was used as a reactant and laser absorber, whereas N 2 was used as a reactant and PTM, thus avoiding any unnecessary contamination source. The same approach was successfully adopted to induce chemical reactivity in P and H 2 , leading to the synthesis of PH 3 and to the discovery of the crystalline van der Waals compound (PH 3 ) 2 H 2 and, more recently, to the synthesis of crystalline arsenic nitride (AsN) from As and N 2 …”

Structural Diversity and Superconductivity in S–P–H Ternary Hydrides under Pressure

“…For example, despite the fact that Ca 2 H 5 lies 20 meV/atom above the convex hull, this binary hydride has been synthesized . Moreover, even though DFT calculations predict that hydrides of phosphorus are not thermodynamically stable under pressure, − a superconducting PH n phase and a van der Waals (PH 3 ) 2 H 2 crystalline compound have been synthesized. Finally, a number of H x S y superconductors have been made, and various stoichiometries including H 3 S, , H 2 S, , HS 2 , H 4 S 3 , H 5 S 2 , exotic Magnéli phases, and self-ionized (SH – )­(H 3 S) + perovskites that may have long modulations , have been proposed.…”