Hydrogen has been considered as one of the most promising energy source for future due to its high-energy density and no air pollutant emission. Water electrolysis into hydrogen and oxygen is an environmentally friendly method to produce hydrogen. Water electrolysis reaction is divided into two half reactions; hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). High overpotential of both HER and OER is the most significant problems to hamper reaction rate and overall efficiency of water electrolysis, which leads to increase in hydrogen production cost. Therefore, exploring active catalysts for HER and OER is one of the major issues in water electrolysis. Platinum (Pt) has been conventionally used as an efficient catalyst for HER. But, its high cost and scarceness is not suitable for a large-scale application of water electrolysis. As for the HER, the electrocatalytic activities of carbide materials, such as molybdenum carbide (Mo₂C), and tungsten carbide (WC), have been remarkable among non-precious metal based catalysts. But, it is very difficult to synthesize nanostructured carbides, which is regarded as a main obstacle for increase in HER activity of such carbide based catalyts.

Herein, we report highly porous Mo₂C and WC catalysts synthesized from a sacrificial leaching for hydrogen evolution reaction. We firstly synthesized Mo₂C and WC composites with cobalt nanoparticles (Co-Mo₂C and Co-WC) using graphitic carbon nitride (g-C₃N₄) as a carbon source, and then leached Co nanoparticles in 0.5 M sulfuric acid (H₂SO₄) solution. Through this sacrificial leaching method, we could successfully synthesize highly porous Mo₂C and WC nanoparticles. Highly porous Mo₂C and WC catalysts exhibited much enhanced HER activities in hydrogen saturated 0.5 M H₂SO₄ solution in comparison to Mo₂C and WC nanoparticles synthesized from conventional carburizing method.

Fig. HER activities of highly porous and conventional Mo₂C nanoparticles.