Hierarchical Polyoxometallate Confined in Woven Thin Films for Single-Cluster Catalysis: Simplified Electrodes for Far-Fetched O₂ Evolution from Seawater

Abstract

The highly anticipated artificial conversion of water to oxygen for the imperishable growth of renewable energy requires efficient water oxidation catalysts (WOCs) to drive the exciting 4e − transformation at low driving potentials. Herein, we describe the freestanding thin film of P 5 Q 7 (TFPQ), where Preyssler [P 5 W 30 O 110 ] 14− (P 5 ) clusters are woven with [CH 3 (CH 2 ) 6 ] 4 N(Br) chains (Q 7 ) to confine P 5 clusters and maximize its catalytic exposure. The TFPQ-supported electrode shows OER at record-low overpotentials at 10 mAcm 2 (η 10 = 130 and 490 mV), rapid migration of electrons (Tafel, 35 and 56 mVdec −1 ), turnover frequency (TOF, 8.55 s −1 ), in alkaline water (1 M KOH), and natural seawater, respectively. Evenly dispersed and confined conducting P 5 clusters with a delocalized charge cloud shows ∼3 times lower η 10 and eventually high OER efficiency than nonconfined clusters. The TFPQ electrodes showed a prolonged stability of minimum 1000 cycles in alkaline water and seawater, without the leaching of true catalytic species P 5 .

Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform

“…On the other hand, hierarchical polyoxometallate thin film has been directly picked up from the air-water interface. [73] Significantly low overpotential (η 10 ), in the range of 130 to 500 mV, at 10 mA/cm 2 current density has been observed with various catalysts. The low charge-transfer resistance at the electrode-electrolyte interface is indicative of apt loading of electrocatalyst, which has been found to be as low as 12 ohms in the case of graphitic carbon electrocatalyst derived from sugarcane bagasse and later doped with Ni.…”

“…The PCE provides opportunities to settle these problems. Although the drop casting, SAM [72] and loading of 2D catalyst film from the air water interface [73] have also been successfully tried over PCE, the PCE has two unique advantages. The probe/ catalysts can either be attached chemically on the polymer matrix (Figure S1) or admixed in the electrode casting slurry or both can be done simultaneously.…”

“…Ru‐triazine COF, [51] Ni based MXene, [89] hierarchical nanostructure, [90] and Ni‐doped graphitic carbon based electrocatalysts [91] were loaded in the blends of nafion by drop casting. On the other hand, hierarchical polyoxometallate thin film has been directly picked up from the air‐water interface [73] . Significantly low overpotential (η 10 ), in the range of 130 to 500 mV, at 10 mA/cm 2 current density has been observed with various catalysts.…”

Functional Nanostructures from Sol–Gel Synthesis Using Keggin Polyoxometallate Phosphotungstic Acid as a Precursor

“…An attractive candidate for the photo- and electrocatalyst in water splitting [i.e., oxygen evolution reaction (OER)] is pure − and chemically doped − tungsten oxide along with closely related nanocomposite heterostructures. − The challenge in the creation of such related nanostructures is the relatively high reactivity and solubility of WO 3 and its derivatives in both acidic and basic media. , Here, in particular, phosphotungstic acid has attracted attention as a possible photocatalyst , and potentially electrocatalyst. However, this compound in its hydrated form is highly soluble in water, which hinders its application.…”