Fe hotspots in the Ni–Ni3B nanocatalyst unravel remarkable cooperativity to boost hydrogen production from ammonia borane with enzyme-like catalysis

Abstract

Cooperative catalysis is a well-known phenomenon exhibited by some enzymes wherein multiple entities function in tandem to catalyze reactions efficiently and/or with selectivity. However, designing advanced heterogeneous catalysts that can cooperatively regulate reactions is exciting, but it is a challenging task. Herein, the fractional incorporation of Fe like hotspots in the Ni–Ni₃B nano-matrices (10% Fe–Ni–Ni₃B) furnishing remarkable cooperativity that can finely regulate the hydrogen production from the chemical hydrogen storage material, ammonia borane (AB), under ambient conditions is unveiled. Experimental evidence and dehydrogenation kinetic studies reveal that Fe acts as an activator by inducing strong electronic communication in the catalyst matrix. These interactions boost the H₂ generation rate to ∼8500 mL min⁻¹ g_catalyst⁻¹ and significantly reduce the activation energy (E_a) to 39.95 kJ mol⁻¹ from 55.14 kJ mol⁻¹ calculated for Ni–Ni₃B alone. The Fe-incorporated catalyst shifts the half-order dehydrogenation kinetics of Ni–Ni₃B to Michaelis Menten-like kinetics, typically observed for enzymes, showing a rate max (R_max) ∼18 000 mL min⁻¹ g_catalyst⁻¹. Heterogeneous catalysts rarely exhibit such a cooperative property and enzyme-like catalysis for a non-enzymatic reaction. The catalyst shows 100% H₂ generation efficiency and a high turnover frequency (TOF) of ∼293 mol_H2 mol_Fe⁻¹ min⁻¹. Upon interaction of dopamine with the Fe active centers, the electronic communications attenuate, diminishing the dehydrogenation rate, and confirming that electronic communication is necessary for cooperative catalysis. This investigation highlights the engineering of materials to induce electronic interactions and cooperativity, which may spur interest in developing inexpensive catalysts for meeting the energy demand.