Schottky junction catalysts boost hydrogen production with non-precious metals in water electrolysis

Electricity-driven water electrolysis has garnered notable attention as an environmentally friendly method for hydrogen production, with high-purity hydrogen being crucial for addressing the energy crisis. Nonetheless, water electrolysis hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) typically require precious metals as electrocatalysts. This limitation has prompted researchers to focus on developing effective non-precious metal catalysts to enhance both the efficiency and cost-effectiveness of water electrolysis.

Carbon nitride(g-C₃N₄) has been widely studied for its tunable semiconducting properties; however, its limited charge mobility and low specific surface area lead to poor catalytic activities for HER and OER. In a study published in the journal Advanced Powder Materials, a team of researchers from Xi’an University of Architecture and Technology in China developed two active Schottky junction electrocatalysts (B–C₃N₄@Fe₃C and S–C₃N₄@Fe₃C) using a targeted doping and an interfacial coupling strategy.

“A strategy that rationally constructs built-in electric fields and space charge regions to enhance the redox reaction kinetics on g-C₃N₄ hollow nanotubes was first proposed,” said the study’s senior corresponding author Sining Yun.

The team’s efforts confirmed that internally supported g-C₃N₄ hollow nanotubes possess abundant active regions that facilitate rapid proton and mass transfer.

“Directed doping with B and S precisely modulated the semiconducting properties of g-C₃N₄, resulting in the formation of typical n-type and p-type band structures,” continued Yun. “This modulation provided a superior platform for constructing surface-functionalized B-C₃N₄@Fe₃C and S-C₃N₄@Fe₃C Schottky junction catalysts.”

The results revealed that the coupling of Fe₃C and g-C₃N₄optimizes the energy level of g-C₃N₄ and changes the interfacial charge distribution of g-C₃N₄@Fe₃C, thus enriching OH^– and H⁺ at the solid-liquid reaction interface. Notably, B-C₃N₄@Fe₃C and S-C₃N₄@Fe₃C catalysts exhibited stable HER activity and high selectivity for the OER under alkaline medium.

“The B-C₃N₄@Fe₃C||S-C₃N₄@Fe₃C pair requires only a low voltage of 1.52 V to achieve efficient water electrolysis at 10 mA cm^-2, highlighting their excellent electrocatalytic activity and promising stability under long-term alkaline water splitting conditions,” said Guangping Yang, first author of the study.