Controllable Synthesis Of Prussian Blue Analogues/derivatives And The Performance On Oxygen Evolution Reaction

Considering the high demand for fossil fuels and their non-renewable nature,it is crucial to find efficient,economical and long-term alternative energy sources.Hydrogen energy is considered as the ultimate fossil fuel alternative because of its high energy density,zero carbon emissions and renewable nature.The electrochemical decomposition of water is the most efficient and environmentally friendly way to produce hydrogen.However,the oxygen evolution reaction（OER）at the anode is a slow half-reaction that requires a large overpotential to exceed the reaction threshold（1.23 V vs.RHE）,significantly hindered the overall performance of electrocatalytic overall water splitting.The OER half-reaction has become a bottleneck for electrocatalytic overall water splitting.Therefore,it is crucial to synthesize highly active electrocatalysts to reduce the reaction activation energy,thus improving the overall water splitting efficiency.Electrocatalysts for OER usually include noble metal and non-precious metal-based materials.It is well known that precious metals are extremely expensive with limited resources.To reduce the cost,there is an increasing interest in exploring non-precious metal-based OER catalysts.However,the performance of non-precious metal-based materials is relatively poor and improving the electrocatalytic performance remains a great challenge.Through previous studies,it was found that porous coordination polymers with specific composition,structure and morphology have great potential in constructing efficient electrocatalysts.Prussian blue analogue（PBA）is a representative cyano-ligand polymer material.the composition of metal ions in PBA is controllable,rich in metal reaction sites,prone to pre-oxidation processes,and can be further modified or converted to metal compounds by chemical processes.PBA has promising applications in electrocatalytic water splitting.In addition,thanks to the unique structural features of PBA,its derived electrocatalysts also have large specific surface area and homogeneous active sites.In this thesis,the authors used PBA and its derivatives as research objects,and utilized optimization strategies such as multi-metal synergy,optimization of electronic structure and construction of amorphous structure to synthesize"pre-catalysts"with excellent performance,which promoted the generation of high-valent metal sites and improved OER performance.The main contents of this thesis include:1.The authors proposed a strategy of two-element modulation at cation and anion sites to synthesize polymetallic Prussian blue analogue pre-catalysts.The catalytic efficiency of OER was greatly improved thanks to the efficient pre-oxidation ability and the multi-metal synergistic effect.Detailed studies have shown that the Ni Cu Co^Ⅱ-Fe^ⅢCo^Ⅲcatalyst contains a polymetallic cation of Co and a mixed Fe ^ⅢCo ^Ⅲcyanide anion,which is favorable for OER catalysis,and the local Co³⁺active site ensures high intrinsic activity as well as optimal polymetallic synergy.After a simple pre-oxidation process,additional high-valence Ni,Cu and Fe ions can be generated as active sites in situ,which significantly improves the OER performance.This work provides new ideas for future catalyst design by simultaneously performing bimetallic ion modulation at both anionic and cationic sites.2.The authors propose an improved molten salt synthesis strategy to achieve synergistic enrichment and surface modification of catalytically active species,and the prepared borate-modified Co Fe spinel oxides can be used as efficient and durable OER catalysts for electrocatalytic water splitting.Physical characterization shows that both molten salt calcination and surface borates can optimize the electronic structure of Co Fe spinel oxides,leading to local enrichment of high-valence metals and enhanced electropositivity,thus improving the intrinsic activity of OER catalysis.The catalyst has various structural advantages such as large surface area and abundant high-valence metal sites.Thanks to its structural advantages,it has excellent electrocatalytic activity such as low overpotential,high current density and small Tafel slope.