Controlled Synthesis of Unconventional Phase Alloy Nanobranches for Highly Selective Electrocatalytic Nitrite Reduction to Ammonia

Abstract

The controlled synthesis of metal nanomaterials with unconventional phases is of significant importance to develop high‐performance catalysts for various applications. However, it remains challenging to modulate the atomic arrangements of metal nanomaterials, especially the alloy nanostructures that involve different metals with distinct redox potentials. Here we report the general one‐pot synthesis of IrNi, IrRhNi and IrFeNi alloy nanobranches with unconventional hexagonal close‐packed (hcp) phase. Notably, the as‐synthesized hcp IrNi nanobranches demonstrate excellent catalytic performance towards electrochemical nitrite reduction (NO2RR), with superior NH3 Faradaic efficiency and yield rate of 98.2% and 34.6 mg h‐1 mgcat‐1 (75.5 mg h‐1 mgIr‐1) at 0 and ‐0.1 V (vs reversible hydrogen electrode), respectively. Ex/in‐situ characterizations and theoretical calculations reveal that the Ir‐Ni interactions within hcp IrNi alloy improve electron transfer to benefit both nitrite activation and active hydrogen generation, leading to a stronger reaction trend of NO2RR by greatly reducing energy barriers of rate‐determining step.

Metal Doped Unconventional Phase IrNi Nanobranches: Tunable Electrochemical Nitrate Reduction Performance and Pollutants Upcycling

“…The chemicals and reagents used in this work are stated in Text S1, SI. The synthetic procedure of hcp phase IrNi nanobranches follows our previous work . First, 4 mg of Ir­(acac) 3 , 4 mg of Ni­(acac) 2 , and 0.5 mg of Cu­(acac) 2 were added into a 12 mL glass vial, and then 4.5 mL of oleylamine plus 0.5 mL of oleic acid were added into the system.…”

“…Herein, unconventional hexagonal close-packed ( hcp ) phase IrNi nanobranches with good electrochemical nitrite reduction performance reported in our previous work were doped with three elements (i.e., Cu, Co, and Ru) of different electronegativities, and the unconventional hcp phase was well maintained after doping. Different dopants result in different nitrate reduction performances.…”

“…The synthetic procedure of hcp phase IrNi nanobranches follows our previous work. 39 First, 4 mg of Ir(acac) 3 , 4 mg of Ni(acac) 2 , and 0.5 mg of Cu(acac) 2 were added into a 12 mL glass vial, and then 4.5 mL of oleylamine plus 0.5 mL of oleic acid were added into the system. Until a homogeneous solution formed, 100 μL of formaldehyde were added.…”