This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Cobalt phosphide (CoP) is a promising alternative to platinum for producing hydrogen from water. However, scientists have struggled to explain why it performs so well.
Computer models have suggested that CoP should become unstable under the conditions used to produce hydrogen, yet experiments show that it remains active and durable in acidic, neutral and alkaline environments. A new study published in the Journal of the American Chemical Society offers an explanation: CoP changes its surface as it produces hydrogen, helping it maintain its performance while protecting itself from damage. Rather than remaining chemically unchanged, the material responds to the electrical voltage applied during water electrolysis.
The chemical species that form on its surface help drive hydrogen production and prevent the catalyst from breaking down. At lower voltages, hydroxyl groups (P-OH) form on the phosphorus sites of the catalyst. These groups help neighboring cobalt atoms activate water and bind hydrogen more effectively.
As the voltage increases, the surface changes again, becoming covered with hydrogen-containing species (Co-H and P-H). This adjustment allows the catalyst to maintain an effective balance between binding and releasing hydrogen across a wide range of pH conditions. Importantly, these surface changes also help protect the material.
The adsorbed hydroxyl and hydrogen species act as a protective layer, limiting oxidation and preventing cobalt and phosphorus from dissolving into the surrounding solution. To investigate this process, the researchers combined AI-assisted analysis of previous studies, computer simulations and laboratory experiments. Their analysis covered 2,282 observations from approximately 886 cobalt phosphide-based catalysts reported in about 700 scientific publications.
They then used computer models to predict how the catalyst's surface would change during operation and tested these predictions using specially prepared CoP nanosheets. Experiments confirmed the predicted surface changes, with advanced spectroscopic techniques detecting the chemical species involved. Additional tests using deuterium, a heavier form of hydrogen, provided further evidence that hydrogen was forming bonds with phosphorus.
Extract — continue reading at the source.
