Insights into Antiperovskite Ni₃ In_1-x Cu_x N Multi-Crystalline Nanoplates and Bulk Cubic Particles as Efficient...

Intrinsic hydrogen evolution reaction (HER) activity and the mechanism of antiperovskite Ni₃ In_1-x Cu_x N bulk cubic particles and multi-crystalline nanoplates are thoroughly investigated. Stoichiometric Ni₃ In_0.6 Cu_0.4 N reaches the best HER performance, with an overpotential of 102 mV in its multi-crystalline nanoplates obtained from the LDH-derived method, and 143 mV in its bulk cubic particles from the citric method. DFT calculation reveals that Ni-In or Ni-Cu paired on the (100) plane serve as primary active sites. The Ni-Cu pair exhibits stronger OH* and H* affinity that correspondingly reduce OH* and H* adsorption free energy. Introducing specific amounts of the Ni-Cu pair, that is In:Cu = 0.6:0.4 in Ni₃ In_0.6 Cu_0.4 N, can optimize OH* and H* adsorption free energy to facilitate water dissociation in the HER process, while avoiding OH* adsorption getting too strong to block active sites. Besides, Ni₃ In_0.6 Cu_0.4 N turns the water adsorption step spontaneous, which may be attributed to the shifted d-band center and polarizing effect from surface In-Cu charge distribution. This work expands the scope for material design in an antiperovskite system by tailoring the chemical components and morphology for optimal reaction free energy and performance.