Constructing transition metal-based heterostructure nanomaterials for electrocatalysis

Abstract

Storing renewable energy into chemical bonds like hydrogen as a carbon-neutral energy carrier to deliver the energy demands is gaining attention. However, the popular hydrogen production route by water electrolysis involves sluggish half-cell reactions, namely, hydrogen and oxygen evolution reaction (HER and OER), urging the unequivocal development of electrocatalysts. Further, the employment of hydrogen in fuel cells involves a multielectron cathodic oxygen reduction reaction (ORR) that governs the overall efficiency of the fuel cells. Therefore, designing efficient alternatives to scarce and expensive Pt and RuO2-based commercial benchmark electrocatalysts is essential. We have rationally designed transition-metal-based monometallic, bimetallic, and nitride-based hybrid carbon nanostructures for the various electrocatalytic reactions. An inexpensive bimetallic (CoCr) system is developed for water splitting, and the activity is found to be better than the monometallic counterparts. To enhance the electroactive surface area, ultrafine Ru nanoparticles are decorated on N-doped carbon and exploited as bifunctional HER and ORR electrocatalysts. Short carbon nanotubes grafted on the N-doped carbon polyhedra anchoring the alloys of Co are synthesized for water splitting catalysis. Further, the role of Mott-Schottky heterojunction formation at the Ru/N-doped carbon interface towards HER activity is elucidated. Finally, an in-situ ammonia-free strategy to obtain CrN is explored as a Pt-free ORR catalyst. The mechanistic insights into the active site and reaction pathway are investigated using experimental analysis and density functional theory (DFT) calculations.