September 7, 2023
By Sade  Agard
 

Chemists discover new way to split water for easier hydrogen

Concept image of water-splitting process.

A team of German chemists based at Münster University has unveiled a potentially groundbreaking water-splitting method that promises to simplify the production of hydrogen.

Their research, recently published in the journal Nature, introduces a photocatalytic method that leverages light energy to activate water, potentially opening up new avenues in chemistry, particularly in the synthesis of compounds from simpler materials.

Splitting water using light
Water splitting, a chemical reaction that disassembles water into its elemental components of oxygen and hydrogen, has long intrigued scientists due to its potential in various fields.

Photocatalysis, on the other hand, harnesses the power of light to drive chemical reactions.

In this innovative method developed by the German research team, triaryl phosphines, a type of organic phosphine with numerous industrial applications, including as light and heat stabilizers, play a significant role in simplifying hydrogen production.

What sets this water-splitting approach apart is its remarkable efficiency in generating hydrogen, a resource viewed as a promising energy solution for the future.

Moreover, hydrogen plays an essential role in forming various crucial compounds.

The challenge in splitting water lies in its inherent stability, making the separation of hydrogen and oxygen atoms a complex endeavor. A catalyst is typically required to activate water for this process to occur.

Led by Professor Armido Studer from the university's Institute of Organic Chemistry, the team devised a photocatalytic process to activate water, diverging from the conventional use of transition metal complexes commonly employed in such reactions.

In their novel approach, the researchers used triaryl phosphines instead. Under gentle reaction conditions, light emitted by an LED facilitates the transfer of a hydrogen atom to a phosphine-water radical cation.

Radicals are known for their high reactivity, and the phosphine-water radical cation excels as an intermediate for activating water. Consequently, hydrogen atoms can be readily separated and transferred to a substrate.

In a Debrief article, Professor Studer explained that their system "offers an ideal platform for investigating unresearched chemical processes that use the hydrogen atom as a reagent in synthesis."

The implications of this breakthrough in water splitting are vast and extend to multiple scientific domains. For instance, this development may yield transformative applications in the realm of material sciences, agriculture, and pharmaceutical research.

As the scientific community further explores this innovative water-splitting technique, it will be intriguing to observe how various fields of study utilize its simplicity and efficiency for advancement.

The complete study was published in Nature and can be found here.

Study abstract:

Transition metal (oxy)hydroxides are promising electrocatalysts for the oxygen evolution reaction1,2,3. The properties of these materials evolve dynamically and heterogeneously4 with applied voltage through ion insertion redox reactions, converting materials that are inactive under open circuit conditions into active electrocatalysts during operation5. The catalytic state is thus inherently far from equilibrium, which complicates its direct observation. Here, using a suite of correlative operando scanning probe and X-ray microscopy techniques, we establish a link between the oxygen evolution activity and the local operational chemical, physical and electronic nanoscale structure of single-crystalline β-Co(OH)2 platelet particles. At pre-catalytic voltages, the particles swell to form an α-CoO2H1.5·0.5H2O-like structure—produced through hydroxide intercalation—in which the oxidation state of cobalt is +2.5. Upon increasing the voltage to drive oxygen evolution, interlayer water and protons de-intercalate to form contracted β-CoOOH particles that contain Co3+ species. Although these transformations manifest heterogeneously through the bulk of the particles, the electrochemical current is primarily restricted to their edge facets. The observed Tafel behaviour is correlated with the local concentration of Co3+ at these reactive edge sites, demonstrating the link between bulk ion-insertion and surface catalytic activity.