Highly Efficient Non-noble Metal Hydrogen Evolution Catalysts

Brookhaven National Laboratory Background
Among various hydrogen (H2) production methods, high purity of hydrogen can be obtained by the eco-friendly water electrolysis. Electrocatalytic systems for H2 generation by water electrolysis typically incorporate expensive noble metals such as platinum in the catalysts because of their low overpotential and fast kinetics for driving the hydrogen evolution reaction (HER). Guided by the activity for the evolution of hydrogen as a function of the metal-hydrogen (M-H) bond strength and exploiting the decrease in the overpotential by carrying out HER in acidic media, researchers at Brookhaven have developed a series of novel non-noble metal hydrogen evolution catalysts. In electrocatalytic experiments, nickel-molybdenum (NiMo) nitride nanosheets on a carbon support (NiMoNx/C) prepared according to the described method demonstrates efficient HER activity.
Technology Overview
The NiMoNx/C catalyst is synthesized by reduction of a carbon-supported ammonium molybdate and nickel nitrate mixture in an oven in H2 at 400 oC, and subsequent reaction with ammonia at 700 oC. During this process, the ammonium molybdate and nickel nitrate precursors are reduced to NiMo metal particles by H2, and then they are mildly transformed to NiMoNx nanosheets by reaction with ammonia . HER activities of the synthesized NiMoNx/C and MoN/C were investigated in HClO4 solution using a traditional three-electrode setup and compared to the commercial Pt catalyst ( & ). Linear voltammetry in acidic solution demonstrated that the NiMoNx/C catalyst is fairly corrosion resistant in the electrolyte; it showed a low current density up to a potential of 0.84 V versus RHE, indicating that the presence of nitrogen significantly stabilized NiMoNx nanosheets in an acidic medium. To assess the long-term durability of the NiMoNx catalyst, potential sweeps were conducted from -0.3 to +0.9 V for 2000 cycles. After cycling, the catalyst retained a polarization curve similar to that before testing (Figure 3), indicating that the NiMoNx catalysts maintained its unique nanosheet structure over a long time in an acidic environment. With highly exposed reactive sites and a synergism among its components, the NiMoNx/C catalyst exhibited high HER electrocatalytic activity with a high exchange current density, low over potential (78 mV) and a small Tafel slope (35 mV dec−1). Overall, this technology offers an efficient heterogeneous electrocatalytic hydrogen evolving system using earth-abundant inexpensive components.
Further Details
Journal Article
Most of the current electrocatalytic water splitting system use noble-metal catalysts, particularly platinum. Replacement with considerably less expensive non noble metal catalysts that are highly active and stable can result in new electrolyzers at a lower cost. BNL catalysts are shown to be stable, active for HER and were made using inexpensive metal ions.
Companies in the renewable energy business, manufacturers of electrolyzers, and electrocatalyst providers may be interested in this new hydrogen evolution reaction catalyst.
Seeking industry partner to develop and commercialize the technology through licensing.
BNL 2012-021

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