Overall electrochemical splitting of water at the heterogeneous interface of nickel and iron oxide

Abstract

Efficient generation of hydrogen from water-splitting is an underpinning chemistry to realize the hydrogen economy. Low cost, transition metals such as nickel and iron-based oxides/hydroxides have been regarded as promising catalysts for the oxygen evolution reaction in alkaline media with overpotentials as low as ~200 mV to achieve 10 mA cm−2, however, they are generally unsuitable for the hydrogen evolution reaction. Herein, we show a Janus nanoparticle catalyst with a nickel–iron oxide interface and multi-site functionality for a highly efficient hydrogen evolution reaction with a comparable performance to the benchmark platinum on carbon catalyst. Density functional theory calculations reveal that the hydrogen evolution reaction catalytic activity of the nanoparticle is induced by the strong electronic coupling effect between the iron oxide and the nickel at the interface. Remarkably, the catalyst also exhibits extraordinary oxygen evolution reaction activity, enabling an active and stable bi-functional catalyst for whole cell water-splitting with, to the best of our knowledge, the highest energy efficiency (83.7%) reported to date.

Etching‐Doping Sedimentation Equilibrium Strategy: Accelerating Kinetics on Hollow Rh‐Doped CoFe‐Layered Double Hydroxides for Water Splitting

“…What is more, this electrolyzer exhibits good catalytic durability, sustaining constant electrolysis at 10 mA cm −2 or up to 10 h without obvious degradation ( Figure S22, Supporting Information). All in all, the performance displaying in the electrolyzer of Rh-doped CoFe-ZLDH is much better than many previous works, such as Ni-Fe NP, [39] a-RuTe 2 porous nanorods (a-RuTe 2 PNR), [54] Pt-GT-1 + 20% Ir/C, [8] Ni 2 P-NiP 2 HNPs+NiFe-LDH, [55] NiFeRu-LDH, [24] N-Ni 3 S 2 /NF, [56] Cu@NiFe-LDH, [57] CoFeZr oxides/NF, [58] and Rh NP/C+NiFe-LDH, [59] which was shown in Figure 4d and Table S3 in the Supporting Information.…”

“…Tafel plots of the corresponding polarization curves are a feasible method to study the HER reaction pathway and kinetics of the electrocatalysts. [39,40] The smaller Tafel slope, the faster reaction rate. As shown in Figure 3b, the Tafel slope of Rh doped CoFe-ZLDH is as low as 42.8 mV decade −1 , which is much smaller than Rh-doped CoFe-LDH (63.6 mV decade −1 ), CoFe-ZLDH (100.1 mV decade −1 ), CoFe-LDH (84.9 mV decade −1 ), and NF (103.7 mV decade −1 ).…”

“…Considering these results, the reaction process driven by Rh doped CoFe-ZLDH follows the Volmer-Heyrovsky mechanism to achieve a rapidly increasing hydrogen evolution rate under the application of voltage. As shown in Figure 3c and Table S2 in the Supporting Information, Rh-doped CoFe-ZLDH outperforms many other previously reported state-of-art HER electrocatalysts, such as Rh 2 P, [41] L-Ag, [42] single atomic Co supported on phosphorized carbon nitride nanosheets (Co 1 /PCN), [43] NiMoO x -Ni(OH) 2 /NF, [44] interface catalyst consisting of atomic cobalt array covalently bound to distorted 1T MoS 2 nanosheets (SA Co-D 1T MoS 2 ), [45] Pt clusters in hollow mesoporous carbon spheres (Pt 5 /HMCS), [46] Ni-Fe nanoparticle (Ni-Fe NF), [39] oxygen vacancy enrich CoFe 2 O 4 (r-CFO), [47] CoFeP TAPs/Ni, [48] nickel-molybdenum-nitride nanoplates on carbon fiber cloth (Ni-Mo-N/CFC), [40] Ru SA -N-S-Ti 3 C 2 T x , [9] W-CoP NAs-CC, [49] MoP@NCHs-900, [50] Co 9 S 8 @C, [51] and Co 0.31 Mo 1.69 C/MXene/NC. [52] The cyclic voltammetry (CV) method was utilized to calculate the electrochemical double-layer capacitance (C dl ) to reflect the electrochemical active area (ECSA).…”

Engineering Facets and Oxygen Vacancies over Hematite Single Crystal for Intensified Electrocatalytic H2O2 Production

“…(α‐Fe 2 O 3 ), a mineral with high abundance and stability, has been proven to be active as an electrocatalyst. [ 26,27 ] However, α‐Fe 2 O 3 is seldom used for oxygen reduction in fuel cells because of its sluggish O 2 adsorption and weak capacity for cracking OO bond, [ 28,29 ] suggesting that it may be a potential candidate for the reduction of O 2 to H 2 O 2 . In particular, the {001} facet is expected to be selective for H 2 O 2 production because this surface, which is covered with oxygen atoms, is weak in terms of its capacity for O 2 adsorption and OO cleavage.…”

Alkali‐Etched Ni(II)‐Based Metal–Organic Framework Nanosheet Arrays for Electrocatalytic Overall Water Splitting

“…It is worth noting that the catalyst has a new peak at 857.6 eV after test, which is assigned to the formation of NiOOH active sites during electrocatalytic process. [45] The creation of defects for tailoring the electronic structure of MOFs and correspondingly improving water splitting performance is then demonstrated by theoretical calculation. The etching treatment results in that the D-Ni-MOF possesses highly open Ni active sites that NiO(OH) for electrocatalysis, owing to the breaking of the NiO bonds between metal-oxide layers and BDC ligands ( Figure S23-S25, Supporting Information).…”