A novel non-Pt based catalyst designed for efficient alkaline hydrogen evolution

As a new form of renewable and clean energy, hydrogen is characterized by its superb energy density, exceptional conversion efficiency, abundant storage and environmentally-friendliness. Electrocatalytic water splitting to produce hydrogen is widely considered as an efficient and attractive technology for the production of renewable energy. To accelerate the sluggish reaction dynamics for hydrogen evolution reaction (HER), particularly in basic electrolytes, massive research efforts have been invested indeveloping high-performance HER electrocatalysts in recent years.

At present, Pt-based materials remain as the benchmark for HER catalysts,but high cost and low abundance poses a tremendous barrier to their extensive applications. Thus, developing inexpensive and efficient electrocatalysts for HER from alkaline water electrolysis is of paramount importance for renewable and sustainable energy.

The research team led by Prof. HOU Yang of the College of Chemical and Biological Engineering has made major progress in research into alkaline water electrolysis. They have developed a novel kind of hybrid electrocatalyst comprised of atomically dispersed Ni–Nxspecies anchored porous carbon (Ni-N-C) matrix with embedded Ni nanoparticles for HER, which is synthesized via the pyrolysis of hydrothermally prepared supermolecular composite of dicyandiamide and Ni ions followed by acid etching treatment. The resulting Ni NP|Ni-N-C hybrid, possessing a strong coupling effect and high surface area of 140 m2g−1, exhibits an excellent HER catalytic activity in basic media, featured by an overpotential of 147 mV to attain 10 mA·cm−2 with a low Tafel slope of 114 mV dec−1, comparable to the state-of-the-art heteroatom-doped nanocarbon catalysts, and even outperforming those reported for other transition-metal-based compounds.

Experimental observations and theoretical calculations reveal that the presence of Ni nanoparticles can optimize the surface states of Ni−Nx active centers and reduce the energy barriers of dissociated water molecules, which synergistically improve the OH− adsorption towards promoted HER kinetics. Using the hybrid served as both the cathode and anode, an alkali electrolyzer delivers a current density of 10 mA cm−2 at a low cell voltage of 1.58 V, outdoing the integrated Ir/C–Pt/C benchmark catalysts for sufficiently high over potentials.

The novel metal NP embedded in the metal-N-C hybrid electrocatalysts will pave a fascinating way to develop highly active cost-effective catalysts for other potential electrochemical applications, including nitrogen fixation, CO2 reduction, and oxygen reduction.

Relevant findings are published in the journal of Energy and Environmental Science.