Interface Engineering via Ti3C2Tx MXene Enabled Highly Efficient Bifunctional NiCoP Array Catalysts for Alkaline Water Splitting.

Developing a non-noble metal-based bifunctional electrocatalyst with high efficiency and stability for overall water splitting is desirable for renewable energy systems. We developed a novel method to fabricate a heterostructured electrocatalyst, comprising a NiCoP nanoneedle array grown on Ti3C2Tx MXene-coated Ni foam (NCP-MX/NF) using a dip-coating hydrothermal method, followed by phosphorization. Due to the abundance of active sites, enhanced electronic kinetics, and sufficient electrolyte accessibility resulting from the synergistic effects of NCP and MXene, NCP-MX/NF bifunctional alkaline catalysts afford superb electrocatalytic performance, with a low overpotential (72 mV at 10 mA cm-2 for HER and 303 mV at 50 mA cm-2 for OER), a low Tafel slope (49.2 mV dec-1 for HER and 69.5 mV dec-1 for OER), and long-term stability. Moreover, the overall water splitting performance of NCP-MX/NF, which requires potentials as low as 1.54 and 1.76 V at a current density of 10 and 50 mA cm-2, respectively, exceeded the performance of the Pt/C∥IrO2 couple in terms of overall water splitting. Density functional theory (DFT) calculations for the NCP/Ti3C2O2 interface model predicted the catalytic contribution to interfacial formation by analyzing the electronic redistribution at the interface. This contribution was also evaluated by calculating the adsorption energetics of the descriptor molecules (H2O and the H and OER intermediates).

Controlled Electrophoretic Deposition Strategy of Binder-Free CoFe2O4 Nanoparticles as an Enhanced Electrocatalyst for the Oxygen Evolution Reaction.

The kinetic-sluggish oxygen evolution reaction (OER) is the main obstacle in electrocatalytic water splitting for sustainable production of hydrogen energy. Efficient water electrolysis can be ensured by lowering the overpotential of the OER by developing highly active catalysts. In this study, a controlled electrophoretic deposition strategy was used to develop a binder-free spinel oxide nanoparticle-coated Ni foam as an efficient electrocatalyst for water oxidation. Oxygen evolution was successfully promoted using the CoFe2O4 catalyst, and it was optimized by modulating the electrophoretic parameters. When optimized, CoFe2O4 nanoparticles presented more active catalytic sites, superior charge transfer, increased ion diffusion, and favorable reaction kinetics, which led to a small overpotential of 287 mV for a current density of 10 mA cm-2, with a small Tafel slope of 43 mV dec-1. Moreover, the CoFe2O4 nanoparticle electrode exhibited considerable long-term stability over 100 h without detectable activity loss. The results demonstrate promising potential for large-scale water splitting using Earth-abundant oxide materials via a simple and cheap fabrication process.