Amorphous Ni_0.75Fe_0.25(OH)₂‐Decorated Layered Double Perovskite Pr_0.5Ba_0.5CoO_3‐δ for Highly Efficient and Stable Water Oxidation

Abstract

Highly active, durable, and cost‐effective electrocatalysts for water oxidation into oxygen gas hold a key role to realise a range of renewable energy solutions which include water‐splitting and rechargeable metal‐air batteries. Despite its very stable oxygen evolution reaction (OER) performance over large number of cycles, layered double perovskite PrBaCo2O5+δ (PBC) has a rather limited surface area. It is, thus, desirable to have the stability of PBC combined with the higher OER activity obtained by enlarging its surface area. Here, we used micro‐sized PBC particles as the substrate for the deposition of nano‐sized nickel‐iron hydroxide, Ni0.75Fe0.25(OH)2, which led to an order of magnitude improvement in the OER current density at 1.63 V versus the reversible hydrogen electrode for the amorphous Ni0.75Fe0.25(OH)2‐decorated PBC catalyst (A‐Ni0.75Fe0.25(OH)2+PBC), relative to the PBC catalyst. We showed that the crystal ordering of the decoration affects the OER activity, that is, the amorphous decoration provided a higher OER activity than the crystalline decoration by enabling a larger contact area between the catalyst and the aqueous electrolyte. The results we show here could potentially stimulate more innovative future works utilising simple chemical preparation route to realise high‐performance hybrid OER catalysts involving novel constituents.

High Density and Unit Activity Integrated in Amorphous Catalysts for Electrochemical Water Splitting

“…Although perovskite‐based catalysts exhibit extraordinary OER activity in alkaline aqueous solution, the poor surface area of their surfaces places restrictions on scale‐up for application in the OER. Zhou and co‐workers [ 154 ] used micro‐sized PBC (PrBaCo 2 O 5+δ ) particles as the substrate for the deposition of nano‐sized Ni 0.75 Fe 0.25 (OH) 2 by wet impregnation to fabricate a promising catalyst of A‐Ni 0.75 Fe 0.25 (OH) 2 + PBC, which led to an order of magnitude improvement in the OER. Compared with PBC, amorphous Ni 0.75 Fe 0.25 (OH) 2 can magnify the contact area between the electrocatalyst and electrolyte, effectively compensating for the poor surface area of the perovskite, and preferably preserves the excellent stability of the perovskite oxide in the OER.…”

Boosting Overall Water Splitting via FeOOH Nanoflake-Decorated PrBa0.5Sr0.5Co2O5+δ Nanorods

“…Apart from the chemical substitution and nanostructure strategy, surface modification through incorporating other efficient electrocatalysts is also envisioned to generate synergistically active sites for promoting electrochemical performance . As known, FeOOH is reported to show potential promise towards water splitting on account of its low-cost and open-structure. − Unfortunately, the pristine FeOOH usually exhibits inferior activity due to its extremely low electrical conductivity and strong bonding between the surface active sites and the OH – group, which hinders its complete activation. , In recent studies, hybridizing nanosized FeOOH on conductive materials (e.g., Ni foam (NF), carbon nanotube, metal/metal oxide) as hybrid catalysts have been proved to exhibit excellent OER activities. − The matrices not only enhance the electrical conductivity of the composite catalysts, but also provide a high electrochemical surface area (ECSA).…”

“…The PBSC nanorods with an average diameter of 100 nm are obtained by an electrospinning method with a large electrochemically active surface area, while the FeOOH layer is fabricated via atomic layer deposition (ALD) of ZnO and subsequent sacrificial template-accelerated hydrolysis process. The amorphous FeOOH layer with controlled thickness could guarantee uniform growth on topmost of the PBSC surface, and the amorphous component is found to be more electrochemically active relative to its crystalline structure experimentally. ,, Benefiting from the hierarchical nanostructure as well as the synergetic catalytic effect of FeOOH and PBSC, the optimized PBSC@FeOOH-20 shows competitive activity for both the OER and HER in alkaline conditions. As a result, by employing PBSC@FeOOH-20 as both cathode and anode in alkaline media, a water splitting current density of 10 mA cm –2 is achieved at 1.638 V with good long-term durability.…”

“…Apart from the chemical substitution and nanostructure strategy, surface modification through incorporating other efficient electrocatalysts is also envisioned to generate synergistically active sites for promoting electrochemical performance. 38 As known, FeOOH is reported to show potential promise towards water splitting on account of its low-cost and open-structure. 39−41 Unfortunately, the pristine FeOOH usually exhibits inferior activity due to its extremely low electrical conductivity and strong bonding between the surface active sites and the OH − group, which hinders its complete activation.…”

CuO Nanorod Arrays Shelled with Amorphous NiFe Layered Double Hydroxide Film for Enhanced Electrocatalytic Water Oxidation Activity

“…Hydrogen (H 2 ) is considered an ideal alternative energy to replace fossil fuels because of its high energy density and environmentally friendly quality. − Electrocatalytic water splitting is one of the most appealing and sustainable approaches for hydrogen production from aqueous solution and has attracted tremendous interests. − However, the overall efficiency of water splitting is greatly hindered by one of its half reactions: the oxygen evolution reaction (OER), which involves a complicated 4H + /4e – transfer process and suffers from sluggish reaction kinetics. − Undoubtedly, the development of efficient water oxidation catalysts (WOCs) is thus of great importance. Currently, some noble oxides including iridium dioxide (IrO 2 ) and ruthenium dioxide (RuO 2 ) are considered to be state-of-the-art, but their industrialized application is considerably restricted by the low abundance and high cost of these precious metals. − Hence, WOCs based on first-row transition metal oxides that contain Co, − Ni, − Fe, − Mn, − or Cu − elements have been widely investigated as the competitive alternatives due to their low cost and unique electronic structure for ion/intermediate absorption. − …”