Exploring the new electrocatalyst based on pyrochlore manganese phosphate/graphene composite for hydrogen evolution and oxygen evolution reaction: An experimental and computational study

An advanced energy conversion technology of water splitting involves two half-reactions of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this work, we synthesized pyrochlore manganese phosphate (Mn2P2O7) nanoplatelets by a simple coprecipitation method and made a composite with two-dimensional graphene nanosheets (GNS) through the ultrasonication process. Various characterization techniques like PXRD, FT-IR, Raman, XPS, SEM, and HR-TEM confirmed the formation of Mn2P2O7-GNS composite material. The catalyst reveals outstanding performance towards HER activity with 0.333 V (vs. RHE) in an acidic medium and OER activity with 1.47 V (vs. RHE) in an alkaline medium at a current density of 10 mA/cm2. The combined experimental study with DFT calculations reveals that the superior electrochemical action may originate from the synergistic effects associated with the high electronic conductivity of GNS and the interfacial belongings formed within Mn2P2O7 and GNS. Also, the GNS plays an essential role in the composite to prevent the aggregation of nanoplatelet particles, thereby increasing active sites and reducing the overpotential. This work proposed recent advances of Mn2P2O7-GNS based materials modified on glassy carbon electrode (GCE) as a stable and durable bifunctional electrocatalyst for the perspectives of the future development of a clean energy landscape.