Introducing High‐Valence Iridium Single Atoms into Bimetal Phosphides toward High‐Efficiency Oxygen Evolution and Overall Water Splitting

Abstract

Single atoms are superior electrocatalysts having high atomic utilization and amazing activity for water oxidation and splitting. Herein, this work reports a thermal reduction method to introduce high‐valence iridium (Ir) single atoms into bimetal phosphide (FeNiP) nanoparticles toward high‐efficiency oxygen evolution reaction (OER) and overall water splitting. The presence of high‐valence single Ir atoms (Ir4+) and their synergistic interaction with Ni3+ species as well as the disproportionation of Ni3+ assisted by Fe collectively contribute to the exceptional OER performance. In specific, at appropriate Ir/Ni and Fe/Ni ratios, the as‐prepared Ir‐doped FeNiP (Ir25‐Fe16Ni100P64) nanoparticles at a mass loading of only 35 µg cm−2 show the overpotential as low as 232 mV at 10 mA cm−2 and activity as high as 1.86 A mg−1 at 1.5 V versus RHE for OER in 1.0 m KOH. Computational simulations confirm the vital role of high‐valence Ir to weaken the adsorption of OER intermediates, favorable for accelerating OER kinetics. Impressively, a Pt/C||Ir25‐Fe16Ni100P64 two‐electrode alkaline electrolyzer affords a current density of 10 mA cm−2 at a low cell voltage of 1.42 V, along with satisfied stability. An AA battery with a nominal voltage of 1.5 V can drive overall water splitting with obvious bubbles released.

Constructing Amorphous–Crystalline Interfaces of Nickel–Iron Phosphides/Oxides for Oxygen Evolution Reaction

“…26 More importantly, the peak area ratio of Ni 3+ /Ni 2+ is increased from 0.56 to 0.81, and the increase of Fe 3+ /Fe 2+ is slightly from 0.54 to 0.68, revealing that the surface amorphous metal phosphides convert into metal oxides/oxyhydroxides under strong anodic oxidation in the OER process according to previous reports. 40,41 Furthermore, the P 2p spectra (Figure 5c) suggest the existence of only oxidized phosphate species after OER tests, which further implies the formation of MO x /MOOH (M = Ni, Fe). Notably, NiFe oxides/oxyhydroxides with higher average valence states have been demonstrated as efficient OER electrocatalysts in an alkaline electrolyte because of the synergistic effect between Ni and Fe, 42−45 which could adjust the affinity of O on the surface catalytic sites to an optimal value and promote the generation of O−O bonds and oxygen evolution.…”

Doping Ru on FeNi LDH/FeII/III–MOF heterogeneous core–shell structure for efficient oxygen evolution

“…S10, S11 and Table S2 †). 18,28,31,44,[54][55][56][57][58][59][60][61][62][63] Stability tests under high current density were also performed on Ru@FeNi LDH/MOF supported on carbon paper. As shown in Fig.…”

Electronic Structure Regulated Nickel-Cobalt Bimetal Phosphide Nanoneedles for Efficient Overall Water Splitting

“…However, the dual functionality of these catalysts is still a challenge for practical application. Electronic structure regulation by doping heterogeneous elements is a beneficial method to enhance the electrocatalytic performance of nickel-based or cobaltbased phosphides [22][23][24][25][26]. For instance, W, Fe-doped CoP nanosheets exhibit significant improvement in OER performance (η 10 = 290 mV) owing to the adjusted electronic structure by the incorporation of duplex metal, while its HER performance still has a lot to improve (η 10 = 130 mV) due to the higher H* desorption energy barrier [27].…”