Researchers from the Universities of Manchester and Warwick have finally solved the long-standing mystery of why graphene is so much more permeable to protons than theory expects.

Ten years ago, scientists from the University of Manchester demonstrated that graphene is permeable to the protons in the nuclei of hydrogen atoms. The unexpected result caused controversy in the community because the theory predicted that it would take billions of years for a proton to penetrate the dense crystal structure of graphene. This led to the assumption that the protons were penetrating through holes in its structure, not the crystal lattice itself.

In the journal Nature, the University of Warwick led by Professor Patrick Unwin and Dr. The results of a collaboration between Marcelo Losada-Hidalgo and the University of Manchester led by Professor André Geim report proton movement measurements with ultra-high spatial resolution. Prove that perfect proton crystals exist through graphene. Unexpectedly, the protons are greatly accelerated around the nanoscale wrinkles and ripples in the crystal.

This discovery could accelerate the development of the hydrogen economy. The expensive catalysts and sometimes environmentally friendly membranes currently used for hydrogen production and use could be replaced with more sustainable 2D crystals, reducing carbon emissions and producing green hydrogen, contributing to Net Zero.

The team used a technique known as scanning electrochemical cell microscopy (SECCM) to measure the smallest currents of protons collected from nanometer-sized regions. This allowed the researchers to visualize the spatial distribution of proton currents across graphene membranes. If the transport of protons occurred through holes, as some scientists hypothesize, the currents would be concentrated in a few isolated places. No such isolated spots were found, which excludes the presence of holes in the graphene membranes.

Doctors Segun Wahab and Enrico Daviddi, lead authors of the paper, commented: “We were surprised that we did not see any defects in the graphene crystals. Our results provide microscopic evidence that graphene is permeable to protons.”

Unexpectedly, proton currents were discovered to accelerate around nanometer-sized wrinkles in the crystals. The scientists discovered that this happens because the wrinkles effectively “stretch” the graphene lattice, thereby providing more space for protons to penetrate the pristine crystal lattice. This observation now reconciles experiment and theory.

Dr. Lozada-Hidalgo said: “We’re actually expanding a grid at the atomic scale, and we’re seeing a higher current in the elongated interatomic spaces in that grid, which is incredible.”

Professor Unwin said: “These results demonstrate that the SECCM developed in our lab is a powerful method for obtaining a microscopic understanding of electrochemical interfaces, which opens up exciting opportunities for the design of next-generation proton-containing membranes and separators.”

The authors are inspired by the potential of this discovery to create new hydrogen-based technologies.

Dr. Lozada-Hidalgo said: “Using the catalytic activity of wavelets and folds in 2D crystals is a fundamentally new way of accelerating ion transport and chemical reactions. This could lead to the development of low-cost catalysts for hydrogen-related technologies.” Source