Theoretical and experimental investigation on electrostatic field dynamics of Co3O4@NiPx electrocatalyst with core shell structure in overall water splitting reactions

Abstract

Transition metal phosphides (TMPs) with platinum like electronic structures are becoming a potential choice to constructing bifunctional catalysts operated under alkaline conditions. Nevertheless, the instability of TMP prevents a further enhancement on its electrocatalytic activity. In this study, the Co3O4 core was first formed through thermal annealing in air, and then the outer NiPx layer was formed through the P-method, cleverly integrating the properties of the inner and outer materials and supplementing respective shortcomings, ultimately improving their water decomposition performance. When Co3O4@NiPx is used as a bifunctional electrocatalyst in 1 M KOH, the HER performance is determined to be 99 mV (η10). The electrocatalytic performance for oxygen evolution reaction (OER) is 249 mV (η50). For overall water decomposition, the bifunctional electrocatalysts Co3O4@NiPx coupled dual electrode alkaline battery only requires 1.51 V to obtain η50 and maintains its excellent electrocatalytic ability for 50 h. Finally, a combination of electrostatic field theory analysis and DFT calculations was used, the results indicated that the stability of core–shell materials can be significantly enhanced through Co3O4 core and internal electron redistribution by P atoms, thereby improving catalytic performance. The greatly improved electrochemical performance of Co3O4@NiPx indicates the rationality of the design and synthesis of the core–shell structure. The combination of electrostatic field theory analysis and DFT calculation also further reveals the rationality of its internal electrocatalytic mechanism.