Nano-confinement may be the key to improving hydrogen production

Researchers at Lawrence Livermore National Laboratory (LLNL) have discovered a new mechanism that can increase the efficiency of hydrogen production through water splitting.

This research, published in ACS Applied Materials and Interfacesappeared on the cover of the journal and provides new insights into the behavior of water reactivity and proton transfer under extreme confinement, suggesting possible strategies to improve the performance of electrocatalysts for hydrogen production while protecting the catalyst from degradation.

The production of hydrogen through the photoelectrochemical splitting of water has long been considered a “Holy Grail” of electrochemistry. A key to the widespread adoption of this technology is the development of an active, stable, yet affordable electrocatalytic system.

Together with Columbia University and the University of California, Irvine, LLNL scientists have developed a new strategy to improve the balance between the activity and stability of electrocatalysts by encapsulating the catalyst with ultra-thin, porous layers of titanium dioxide.

The Columbia team led by Daniel Esposito previously reported that nanoporous oxides covering platinum nanoparticles can improve the stability of the system without compromising catalytic activity, contrary to the widely held view: covering the catalyst surface will severely compromise catalytic activity. . The nanoporous structure also appears to improve selectivity by favoring water splitting reactions over competing processes.

In their study, the LLNL scientists used advanced molecular dynamics (MD) simulations with a machine learning potential derived from first-principles calculations. This platform enables exploration of the potential energy surface and reaction kinetics with extraordinary precision at scales beyond the reach of conventional first-principles approaches. Simulations revealed that water confined within nanopores smaller than 0.5 nanometers shows significantly altered reactivity and proton transfer mechanisms. In particular, the team observed that insulation lowers the activation energy for proton transport.

“Our findings show that in extremely confined environments, the activation energy for water dissociation decreases, leading to more frequent proton transfer events and fast proton transport,” said Hyuna Kwon, a materials scientist in the Simulation Group. LLNL Quantum and the Laboratory for Energy Applications for the Future (LEAF). “This knowledge could pave the way for the optimization of porous oxides to improve the efficiency of hydrogen production systems by tuning the porosity and surface chemistry of the oxides.

“Our study therefore represents the collective efforts of three DOE centers and underscores LLNL’s commitment to improving renewable hydrogen production technologies,” Kwon said.

Other LLNL co-authors on the paper include Marcos Calegari Andrade, Tuan Anh Pham, and Tadashi Ogitsu.