The oxygen evolution reaction (OER) from water could be important for future energy supply and requires effective catalysts. Since the commonly used noble-metal oxides are highly expensive, the discovery and development of earth-abundant alternatives would be useful. Black phosphorus (BP) is the least reactive allotrope of phosphorus and is obtained from heating white phosphorus under high pressure.

Xiang Qi, Xiangtan University, China, Han Zhang, Shenzhen University, China, and colleagues have analyzed the catalytic activity of few-layer BP nanosheets synthesized from bulk BP by liquid exfoliation. The team investigated the OER performance in a standard three-electrode cell with potassium hydroxide (KOH) as the electrolyte for different OH^– concentrations.

The researchers found that compared to bulk BP, the electrochemical activity of BP nanosheets is greatly improved and that BP nanosheets show OER properties comparable to metal oxide-based catalysts, such as IrO₂. Hence, the reduction of the thickness of BP is an effective way to generate additional active sites and considerable high electronic mobility. As a further benefit, the BP nanosheets show high stability under alkaline conditions.

• Few-Layer Black Phosphorus Nanosheets as Electrocatalysts for Highly Efficient Oxygen Evolution Reaction,
  Xiaohui Ren, Jie Zhou, Xiang Qi, Yundan Liu, Zongyu Huang, Zhongjun Li, Yanqi Ge, Sathish Chander Dhanabalan, Joice Sophia Ponraj, Shuangyin Wang, Jianxin Zhong, Han Zhang,
  Adv. Energy Mater. 2017.
  DOI: 10.1002/aenm.201700396