Electrochemical water splitting is important for renewable energy technologies, such as hydrogen fuel production and rechargeable metal-air batteries. A variety of earth-abundant and cost-effective electrocatalysts have been developed as catalysts for water electrolysis. However, further improvement of the electrochemical performance remains challenging.

Shi-Zhang Qiao, University of Adelaide, Australia, and colleagues have developed an electrochemical self-templating strategy to prepare hollow Co₃O₄ microtube arrays. CoHPO₄ microrods with relatively low stability were first grown on a nickel foam. A subsequent potentiostat treatment in alkaline media resulted in the transformation of protonated CoHPO₄ microrods into hollow Co₃O₄ microtubes with hierarchical porosity and high surface area.

The resulting self-supported catalysts can be directly used in catalyzing oxygen and hydrogen evolution. In overall water electrolysis, the catalyst provides a current density of 10 mA m^–2 at 400 mV overpotential, along with a high durability. The microtubes surpass the performance of the precious-metal catalysts IrO₂/C and Pt/C.

• Self-Templating Synthesis of Hollow Co₃O₄ Microtube Arrays for Highly Efficient Water Electrolysis,
  Yun Pei Zhu, Tian Yi Ma, Mietek Jaroniec, Shi Zhang Qiao,
  Angew. Chem. Int. Ed. 2016.
  DOI: 10.1002/anie.201610413