Preparation Of Several Metal Hydroxides/Oxides And Their Application In Electrocatalytic Oxygen Evolution Reaction

Oxygen evolution reaction?OER?is an important electrode reaction in many electrochemical energy systems.However,the slow kinetics of OER and the high overpotential greatly limit the energy conversion efficiency,and thus the development of high-performance OER electrocatalysts is of great significance.Noble metal materials such as IrO₂ and RuO₂ are commonly used OER catalysts,but their high cost and scarcity seriously limit their large-scale application.Searching for low-cost and earth-abundant non-precious metal OER electrocatalysts has become a hot spot in recent years.The electrocatalytic activities and stability are expected to be improved by tailoring the morphologies,structures and composition of non-precious metal materials.In this paper,several transition metal hydroxide/oxide OER catalysts were designed and prepared.The electrocatalytic activities and stability of these OER catalysts were improved by precisely tailoring their morphologies,structures and composition.The main contents are as follows:?1?CoMo layered double hydroxides?LDH?with trace Mn,Fe or Ni dopants were grown on carbon nanotubes?CNTs?by one step hydrothermal method.We found that the doping of Ni in CoMo-LDH/CNTs can greatly increase the OER activity.The Ni-doped CoMo-LDH/CNTs showed an OER overpotential of only 230 mV at a current density of 10 mA cm^-2,with a Tafel slope of 62 mV dec^-1.X-ray photoelectron spectroscopy result reveals that optimized element doping leads to a higher Co oxidition state,which contributes to boost the OER performace.In addition,the proposed catalyst can retain 70%of initial activity after 48 h test,indicating its excellent stability.?2?Double perovskite LaFe_xNi_1-x-x O₃?LFNO?nanorods were prepared by a simple hydrothermal method,followed by high temperature calcination.The optimized LFNO,LaFe_0.2Ni_0.8O₃?LFNO-II?achieved a low overpotential of 302 mV at 10 mA cm^-2 and a small Tafel slope of 50mV dec^-1,outperforming those of the commercial Ir/C.The LFNO-II NRs also showed high OER stability with slight current decrease after 20 h.The electrochemical active surface area?ECSA?,X-ray photoelectron spectroscopy?XPS?,and surface valence band spectroscopy?VBS?studies indicated that the enhanced activity was attributed to the improved surface area,high valence state of active center,and strong binding of reactants on catalyst surface.?3?BaCoO₃?BCO?and Ni?Cu?doped BCO(BaNi?Cu?_0.1Co_0.9O₃,BN?C?CO)porous perovskite nanowires were prepared by a simple mixing method at room temperature,followed by low temperature crystallization.The most active catalyst in OER was found to be BNCO,which can achieve a low overpotential of 298 mV at 10 mA cm^-2 and a small Tafel slope of 71 mV dec^-1.The BNCO nanowires also showed high OER stability with no obvious current decrease after 20 h test.XPS results indicated that the tailored electronic properties of the Co active centers by Ni doping were responsible for the enhanced OER activity.