In a groundbreaking experiment, scientists have successfully created a solid binary hydride of gold—a compound composed solely of gold and hydrogen atoms. The discovery came unexpectedly during a series of high-pressure experiments led by researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory, in collaboration with international partners. Their findings, published in Angewandte Chemie International Edition, could transform our understanding of chemistry under extreme conditions.
The initial goal of the research was to observe how hydrocarbons transform into diamonds when subjected to immense pressure and temperature. Using the European X-ray Free Electron Laser (XFEL) facility in Germany, scientists placed hydrocarbon samples on thin layers of gold foil, which was intended only to absorb X-rays and transfer heat. Yet, in addition to forming diamonds, the team observed the unexpected creation of gold hydride.
According to the experiments, compressed gold within hydrocarbons formed gold hydride at pressures exceeding 40 gigapascals (GPa) and temperatures above 1926°C. Lead researcher Mango Frost, a scientist at SLAC, noted: “This was surprising because gold is usually chemically inert and considered unreactive. These results suggest that under extreme conditions, where temperature and pressure effects compete with conventional chemistry, exotic compounds like gold hydride can emerge.”
The methodology involved compressing hydrocarbon samples to pressures greater than those found in the Earth’s mantle, using diamond anvil cells. When heated with XFEL X-ray pulses to nearly 1,900°C, the carbon atoms aligned into a diamond lattice. Simultaneously, hydrogen atoms bonded with gold atoms, forming a stable gold hydride structure. Notably, under these conditions, hydrogen entered a superionic state, freely moving within the rigid gold lattice. This unusual state significantly enhanced the compound’s conductivity, making it particularly intriguing for future applications in materials science and energy research.
Studying hydrogen under such conditions is notoriously challenging because it poorly scatters X-ray radiation. However, in this experiment, hydrogen’s interaction with much heavier gold atoms allowed researchers to trace hydrogen’s influence through X-ray scattering, offering a new window into its behavior.
The implications are profound. Dense hydrogen is believed to exist deep within giant planets and inside stars like the Sun. By observing gold hydride in a laboratory setting, scientists can gain new insights into planetary interiors, stellar fusion processes, and even controlled nuclear fusion technologies on Earth. Moreover, the discovery challenges traditional assumptions about the inertness of gold, proving it can form stable compounds under extreme pressures and temperatures.
In conclusion, the creation of solid gold hydride opens new frontiers in chemistry and astrophysics. This breakthrough not only expands the boundaries of known chemical reactions but also paves the way for revolutionary advancements in understanding materials under extreme conditions. While gold hydride may only remain stable in such environments, the knowledge gained from this research is set to influence future studies of planetary science, energy technology, and advanced materials.
