Carbon-Doped NiO Catalyst For Hydrogen Evolution Reaction

Background

Water electrolysis represents a sustainable and environmentally friendly method to generate hydrogen fuel. Since a proton rich environment is favorable for hydrogen adsorption on a catalyst surface, an acidic medium is preferable for hydrogen evolution reaction (HER).

However, performing HER in an acidic medium limits catalysts to platinum group metals. In addition, a corrosive acidic fog generated by the acidic electrolyte not only contaminates the produced hydrogen gas, but also causes severe chemical corrosion of the catalysts. 

These factors add significant cost for hydrogen generation and pose barriers for constructing large-scale electrolyzers.

Alternatively, the use of alkaline electrolytes, which have a low vapor pressure and result in a relatively mild chemical environment could avoid these issues. Non-platinum group metals such as Ni can be used as electrocatalysts or electrodes with alkaline electrolytes. A major challenge for alkaline water electrolysis is the requirement of an additional water dissociation step (i.e., the cleavage of the strong H–OH bond) for generating the essential H atom intermediates for HER.

The high activation barrier of water dissociation makes HER very sluggish in alkaline medium. For example, Pt typically exhibits two orders of magnitude lower exchange current density in alkaline solution than that in acidic solution. It is therefore critical to develop alkaline HER catalysts that contain both hydrogen adsorption sites as well as water adsorption and dissociation sites.

Technology Description

Transition metal oxides such as NiO are promising alkaline HER catalysts. Since Ni sites in NiO possess incompletely filled d orbitals, Ni sites have been reported to serve as active sites for water adsorption and dissociation in alkaline electrolytes. Nonetheless, the performance of NiO is still not comparable to Pt-based catalysts. One of the possible reasons is lack of hydrogen adsorption sites relative to Ni and Pt. 

This invention creates hydrogen adsorption sites for NiO through heteroatom doping, particularly carbon doping.  Carbon doping creates under-coordinated active Ni sites that are highly favorable for hydrogen adsorption. Experiments show that Carbon-doped NiO achieves an ultralow overpotential of 27 mV at the geometric current density of 10 mA /cm², and a low Tafel slope of 36 mV /dec, representing the best performance among the state-of-the-art NiO catalysts.

Applications

Clean hydrogen production by electrolysis in alkaline medium

Advantages

Best performing NiO catalyst in alkaline medium

Cheaper than platinum electrodes

 Longer lasting electrodes and a cleaner reaction than acidic media

Intellectual Property Information

Related Materials

• Carbon doping switching on the hydrogen adsorption activity of NiO for hydrogen evolution reaction - 01/30/2020