Bulk OsO2 Single Crystals: Superior Catalysts for Water Oxidation

TL;DR

This study successfully synthesized high-quality OsO2 single crystals that demonstrate excellent stability and catalytic performance for water oxidation, challenging the reliance on nanoscaling and emphasizing crystal integrity.

Contribution

First demonstration of stable, high-performance OsO2 single crystals for water oxidation, revealing the importance of crystal quality over nanoscale structures.

Findings

OsO2 single crystals are chemically stable in alkaline solutions.

OsO2 single crystals exhibit comparable or better OER performance than RuO2 nanopowders.

Nanoscaling is not essential; crystal integrity is crucial for stable OER catalysis.

Abstract

Although rutile RuO2 has been a well-known and almost the best oxygen evolution reaction (OER) catalyst, the OER properties for the similar rutile oxide OsO2 with the same group element with Ru have been unknown, mainly due to long-standing synthesis difficulties. In this work, we report the successful synthesis of high-quality OsO2 single crystals, and the ground micrometer-size single crystals are chemically stable in alkaline solutions and exhibit robust OER performance. In sharp contrast, OsO2 nanopowder reacts quickly with KOH solutions and cannot work for OER. Compared with commercial RuO2 nanopowder, the OsO2 single crystals show comparable catalytic current densities, remarkably lower overpotentials at high current densities and better stability. These findings question the universal applicability of nanoscaling and highlight crystal integrity as a key descriptor for achieving stable and efficient OER electrocatalysis.