The Self-healing Performance Of NiCoFe-based Oxygen-evolving Catalyst In Highly Alkaline Conditions

Hydrogen energy is widely recognized as the clean and sustainable energy source and so attracted a huge attention by the research community these days.Electrocatalytic water splitting has become one of the emerging research hotspots providing a promising technology for hydrogen production.Because of its kinetically challenging complex proton-coupled reaction,oxygen evolution reaction?OER?is considered as the core reaction responsible for energy conversion through the aforementioned mechanism.Recently,transition metal?Co,Ni,Fe,Mn,etc.?-based catalysts were spotted under red-light to providing the possibility for the realization of low cost,higher activity and longer stability for OER catalysis.The catalytic performance of Fe/Co/Ni-containing catalysts?NiFe,CoFe,NiCoFe?is specifically higher with their oxides,oxihydrates and non-metallic mixed complexes.It has been noted that the majority of recent studies were focused to enhance the geometric activity of OER catalysts but the improvement with the intrinsic activity and stability aspects were overlooked.Meanwhile,the fundamental understanding of composition-structure-activity relationship required to be explored and understood well to guide the design of practical electrocatalysts.The improvement and application of more progressive ex-and in-situ techniques,have provided for a smart interpretation of the specific role of different elemental species in OER catalyst,but rigorous data analysis is required for the exact and in-depth understanding of the mechanism and to void the differences and deficiencies enrooted by various technical issues.With the matter of catalysts stability exploration,self-healing is considered to be the real way to determine the long-term stability of catalysts against the degradation factors.Currently,the self-healing is only theoretically proposed to be a feasible solution,and nothing has been done yet with the experimentally as OER catalyst operating under highly alkaline conditions.Relying on this,we conduct the investigation on self-healing of nickel iron layered double hydroxide?NiFe-LDH?OER catalyst having higher catalytic activity under alkaline conditions.The self-healing within NiFe-LDH fails because the Fe-catalytic center cannot be redeposited under OER operating potential.Consequently,we introduce Co as catalytic for in-situ Fe redeposition into NiFe-LDH structure,and studied the specific role of each element specie in OER.We synthesized a highly active borate intercalated NiCoFe-LDH catalyst?NiCoFe-B_i?by using a simple electrodeposition method.We achieve the stability of the following three conditions:1000 h OER test without degradation at 10 mA·cm^-2 in a KB_i electrolyte containing Fe???ion?pH 14?;stability without degradation for 200 h at 100 mA·cm^-2 in the same solution;and stability 200 h non-degradation test at 300 mA·cm^-2 in higher alkaline solution?pH 14.9?.The analysis of obtained data indicates the extraordinary self-healing ability of NiCoFe-B_i catalyst against OER degradation factors.