Unveiling the synergistic effect of amorphous CoW-phospho-borides for overall alkaline water electrolysis

Abstract

Amorphous transition-metal-phospho-borides (TMPBs) are emerging as a new class of hybrid bifunctional catalysts for water-splitting. The present work reports the discovery of CoWPB as a new promising material that adds to the smaller family of TMPBs. The optimized compositions, namely Co4WPB5 and Co2WPB1 could achieve 10 mA/cm2 at just 72 mV and 262 mV of overpotentials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1 M KOH. Furthermore, the catalyst showed good performance in a 2-electrode assembly (1.59 V for 10 mA/cm2) with considerable stability (70 h stability, 10,000 operating cycles). Detailed morphological and electrochemical characterizations unveiled insights into the role of all elements in catalyst's improved performance. The presence of W was found to be crucial in improving the electronic conductivity and charge redistribution, making CoWPB suitable for both HER and OER. In computational simulation analysis, two configurations with different atomic environments, namely, CoWPBH and CoWPBO were found to have the lowest calculated overpotentials for HER and OER, respectively. It was found that the surface P-sites in CoWPBH were HER-active while the Co-sites in CoWPBO were OER-active sites. The study presents new knowledge about active sites in such multi-component catalysts that will foster more advancement in the area of water electrolysis.