# Atomic-level interface engineering enables efficient and durable acidic hydrogen evolution of osmium at large current densities

## TL;DR

Scientists designed a new catalyst using osmium and cerium oxide to efficiently and durably produce hydrogen in acidic conditions.

## Contribution

A porous CeO2 support enables atomic-level dispersion and stabilization of osmium for ultra-stable hydrogen evolution.

## Key findings

- The Os single-atom catalyst (OsSA–CeO2) shows over 500 hours of durability at 100 mA cm−2 without performance loss.
- Strong electronic coupling and oxygen vacancies in CeO2 enhance stability and proton supply for hydrogen evolution.

## Abstract

Osmium (Os), the least expensive member of the platinum-group metals, has emerged as a promising alternative to Pt-based catalysts for the hydrogen evolution reaction (HER). However, Os-based electrocatalysts still suffer from poor stability under acidic conditions, despite recent efforts to mitigate H* over-adsorption for improved intrinsic activity. Here, we design a porous CeO2 support that enables the atomic dispersion of Os, forming an Os single-atom catalyst (OsSA–CeO2). Unlike traditional flat-film supports, the porous CeO2 architecture prevents Os aggregation and achieves 100% interfacial anchoring of Os atoms. The resulting strong electronic coupling enables tight anchoring of Os and activates the CeO2 matrix with abundant oxygen vacancies, which facilitate H2O dissociation to sustainably supply protons for rapid consumption at large current densities. Also, the generated OH* species are adsorbed by the oxygen vacancies, thus preventing the Os sites from oxidative dissolution. As a result, OsSA–CeO2 exhibits over 500 h of durability at 100 mA cm−2 without performance decay—surpassing all previously reported Os-based HER catalysts. This work provides a general strategy for achieving complete interfacial anchoring of active metal atoms to enhance catalytic stability without sacrificing activity through support activation.

Porous CeO2 achieves atomic dispersion of Os and strong interfacial coupling, stabilizing Os atoms and activating CeO2 with oxygen vacancies for ultra-stable acidic hydrogen evolution.