Electrocatalytic Activity of Some Cobalt Based Sodium Phosphates in Alkaline Solution. (30th January 2018)

• Record Type: Journal Article
• Authors: Dwibedi, Debasmita; Gond, Ritambhara; Sada, Krishnakanth; Senthilkumar, Baskar; Barpanda, Prabeer
• Is Part Of: MRS advances. Volume 3:Number 22(2018)
• Page Start: 1215
• Page End: 1220
• Publication Date: 2018-01-30
• Subjects: catalytic, -- oxidation, -- combustion synthesis; Electrical engineering -- Congresses; Physics -- Congresses; Materials -- Research -- Congresses; Materials science -- Congresses; 620.11
• DOI: 10.1557/adv.2018.136
• Languages: English
• ISSNs: 2059-8521

Abstract

ABSTRACT: The development of efficient water oxidation catalyst is a major path to realize water splitting systems, which could benefit high performance and cost-effective metal-air batteries, fuel cells and solar energy conversion. To date, the rare crustal abundant platinum group metals rule this sector with Pt-alloys being the best for oxygen reduction reaction (ORR) and ruthenium oxides for oxygen evolution reaction (OER) in acidic solution. However, they show poor stability and are too expensive for large scale applications. Moreover, oxygen reduction in basic solutions can otherwise be catalysed by metal oxide with non-precious earth abundant transition metals (e.g. Fe, Co, Ni). Hence, there is a massive demand to explore noble metal free bifunctional electrocatalysts. In this work, we present the electrocatalytic activity of three cobalt based sodium phosphates namely NaCoPO4 (with one phosphate), Na2 CoP2 O7 (with two phosphate) NaFe2 Co(PO4 )3 (with three phosphate). Synthesized by solution combustion route, all these phosphates confirmed phase purity. NaCoPO4 and Na2 CoP2 O7 adopted orthorhombic structure with Pnma and Pna21 space group respectively; whereas NaFe2 Co(PO4 )3 crystallized in monoclinic (C2/c) framework. Electrocatalytic activity of these cobalt phosphates were inspected by linear sweep voltammetry with rotating disk electrode (RDE). All three showed promising bifunctional activity. In fact, the ORR activities of both orthorhombic cobalt phosphates are comparable to Vulcan carbon and Pt/C. OER activity of Na2 CoP2 O7 overrode other phosphates. The bifunctional activity and good stability of these sodium cobalt phosphates stem from cobalt ions and stabilization of the catalytic centres by the phosphate frameworks. The present work builds a detail structure-property correlation in these phosphate systems and also demonstrates the possibility of utilizing these sodium cobalt phosphates as alternate cost-effective, novel electrocatalysts for efficient OER/ORR activity in alkaline solution.