Chemical scissors snip 2-D transition metal dichalcogenides into nanoribbon

Chemical scissors snip 2-D transition metal dichalcogenides into nanoribbon
Schematic view of scissoring 2-D sheets to nanoribbon.

One of the biggest challenges in making hydrogen production clean and cheap has been finding an alternative catalyst necessary for the chemical reaction that produces the gas, one that is much cheaper and abundant than the very expensive and rare platinum that is currently used. Researchers in Korea have now found a way to ‘snip’ into tiny nanoribbons a cheap and plentiful substance that fits the bill, boosting its catalytic efficiency to at least that of platinum.

Researchers have identified a potential catalyst alternative—and an innovative way to produce them using chemical ‘scissors’—that could make hydrogen production more economical.

The research team led by Professor Sang Ouk Kim at the Department of Materials Science and Engineering published their work in Nature Communications.

Hydrogen is likely to play a key role in the clean transition away from fossil fuels and other processes that produce greenhouse gas emissions. There is a raft of transportation sectors such as long-haul shipping and aviation that are difficult to electrify and so will require cleanly produced hydrogen as a fuel or as a feedstock for other carbon-neutral synthetic fuels. Likewise, fertilizer production and the steel sector are unlikely to be “de-carbonized” without cheap and clean hydrogen.

The problem is that the cheapest methods by far of producing hydrogen gas is currently from natural gas, a process that itself produces the greenhouse gas carbon dioxide-which defeats the purpose.

Alternative techniques of hydrogen production, such as electrolysis using an electric current between two electrodes plunged into water to overcome the chemical bonds holding water together, thereby splitting it into its constituent elements, oxygen and hydrogen are very well established. But one of the factors contributing to the high cost, beyond being extremely energy-intensive, is the need for the very expensive precious and relatively rare metal platinum. The platinum is used as a catalyst-a substance that kicks off or speeds up a chemical reaction-in the hydrogen production process.

As a result, researchers have long been on the hunt for a substitution for platinum—another catalyst that is abundant in the earth and thus much cheaper.

Transition metal dichalcogenides, or TMDs, in a nanomaterial form, have for some time been considered a good candidate as a catalyst replacement for platinum. These are substances composed of one atom of a transition metal (the elements in the middle part of the periodic table) and two atoms of a chalcogen element (the elements in the third-to-last column in the periodic table, specifically sulfur, selenium and tellurium).

What makes TMDs a good bet as a platinum replacement is not just that they are much more abundant, but also their electrons are structured in a way that gives the electrodes a boost.

In addition, a TMD that is a nanomaterial is essentially a two-dimensional super-thin sheet only a few atoms thick, just like graphene. The ultrathin nature of a 2-D TMD nanosheet allows for a great many more TMD molecules to be exposed during the catalysis process

Read more