Annual Review 2024-2025

S P E C T R O S C O P Y G R O U P D I A M O N D L I G H T S O U R C E L I M I T E D 29 A Energy (eV) Normalised (a.u.) CWO CWO-del-48 B Radial Distance (A) FT EXAFS CWO CWO-del-48 C Energy (eV) Normalised (a.u.) CWO CWO-del-48 Co K edge (A) and W L3 edge (C) XANES spectra for CoWO before (red line) and after (blue line) delamination, and corresponding radial distribution fuctions for Co (B) and W (D). D Radial Distance (A) Normalised (a.u.) CWO CWO-del-48 A novel catalyst design for green hydrogen production harnesses the power of water Hydrogen has the potential to play a key role in building low-carbon economies, yet today it is mostly obtained from methane, which releases significant amounts of CO₂. “Green hydrogen,” by contrast, is generated cleanly: renewable electricity drives water electrolysis, splitting H₂O into hydrogen and oxygen. Among the electrolysis methods, proton-exchange- membrane water electrolysis (PEMWE) stands out for its high energy efficiency and fast hydrogen output. Although industrial electrolysis is usually carried out under alkaline conditions, operating in acid can boost efficiency even further. However, most alternatives to the very expensive iridium catalysts break down rapidly in acidic environments. In this work, the research team led by The Barcelona Institute of Science and Technology proposed a solution to acid degradation by stabilising a cheaper and more abundant cobalt catalyst through the deliberate introduction of tungsten. In their work, they demonstrated control over the oxygen evolution reaction (OER) by modulating the interfacial water structure and intermediate species in a delaminated CoW oxide lattice. This is achieved through a delamination strategy where the tungsten is selectively eliminated in a water-hydroxide anion exchange process, as observed by XAS studies, stabilising water and hydroxide species in the cobalt oxide defected network. This water-hydroxide “shielding” prevents cobalt ion dissolution, making the catalyst highly stable and active in PEMWE. The cobalt-based catalyst achieved a threefold improvement in activity, remaining stable for up to 600 hours. While this does not yet match current industrial iridium catalysts, it is a big step forward in the search for cost-effective alternatives. The team is currently working on scaling the synthesis of the material to industrial levels and has applied for a patent. DOI: 10.1126/science.adk9849