Water electrolysis has become a crucial part of sustainable, clean energy generation and it has become very imperative to discover highly active electrocatalysts composed of earth-abundant materials for the oxygen evolution reaction (OER), the most challenging half-cell reaction for water electrolysis. Combinatorial methods has been reported to provide an efficient way to screen and discover material composition for promising OER electrocatalysis. Here, we have investigated a series of binary and ternary mixed metal selenides containing varying compositions of nickel, iron, and cobalt as potential OER electrocatalysts. Specifically, a Ni-Co-Fe ternary phase diagram was used in a combinatorial approach. In our investigation, we have synthesized series of transition metal selenide films containing mixed metal compositions such as Ni_xFe_yCo_zSe₂ utilizing electrodeposition technique on different conducting substrates including Au-coated glass and glassy carbon (GC). We systematically investigated the incorporation of Fe and Co into the Ni_xSe_y film and studied its effect the OER electrocatalytic performance of the Ni-selenide. The structure, morphology, and composition of these new electrocatalysts were characterized by power X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy dispersive analysis (EDS), and Raman spectroscopy. The catalytic activities were studied through electrochemical measurements in alkaline media using the linear sweep voltammetry (LSV) and cyclic voltammetry (CV), while the stability of the catalyst was probed by chromoamperometric studies at a constant potential. In this presentation we will discuss some novel catalyst compositions containing Ni_xFe_yCo_zSe_n, Ni_xCo_ySe₄, and Ni_xFe_ySe₄ which show low onset potentials for O₂ evolution along with exceptional extended stability, and show how optimal doping between Ni:Fe:Co influence the catalytic performance. Specifically, we have observed that increasing Co and Fe concentration progressively improves the catalytic efficiency (Figure 1). The efficiency of each binary (or ternary) metal selenide as OER electrocatalyst is reported by measuring the onset overpotential (η) and overpotential (η) at 10 mA cm^-2 current density which is equivalent to 10% solar energy conversion.^[1]  The systematic exploration of binary and ternary Ni:Co:Fe selenides along with electrochemical studies for catalytic efficiency will be discussed in more details. This study opens up a new avenue to investigate other mixed metal selenide combinations, as well as provide opportunity to understand the effect of each transition metal ion (along with the d-electron occupancy) on the catalyst’s performance. Such knowledge will lead us to be able to finely tune the composition of the catalyst for achieving stability and high efficiency.

Reference:

(1). McCrory, C. C.; Jung, S.; Peters, J. C.; Jaramillo, T. F., Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction. J Am Chem Soc 2013, 135, 16977-87