Grain boundary density and electronic dual modulation of intermetallic Co₂B by Fe doping toward efficient catalyst for oxygen evolution reaction

Developing the high-performance intermetallic bi–metal boride OER catalysts with a high density of grain boundaries and appropriate electronic structure is still a challenge. Herein, we synthesized an intermetallic (Fe_xCo_1−x)₂B OER catalyst (GB-(Fe_xCo_1−x)₂B) with controllable grain boundary densities by a facile ball-milling method. Benefiting from the modulation of both grain boundary density and electronic structure, the GB-(Fe_0.66Co_0.34)₂B supported on reduced graphene oxide shows a low OER overpotential of 221 mV at a current density of 10 mA cm⁻² and Tafel slope of 38.2 mV dec⁻¹. The experimental and theoretical calculated methods demonstrate that the Fe introduction into the intermetallic Co₂B catalyst can produce the higher grain boundary density and modulate the electronic structure, respectively. This work provides a promising insight in understanding the synergetic effects in bimetallic for GB-(Fe_xCo_1−x)₂B systems and supports a new strategy to explore other efficient catalysts with a high density of grain boundaries.