Preparation Of Coni-based Bimetallic Composite Catalysts And Performance Of Overall Water Splitting

Hydrogen?H₂?has been considered as the most promising energy with environmental-benignity,high energy density and purity characteristics.Among the many hydrogen production methods,the electrolysis water hydrogen production technology can use the power generated by intermittent energy sources,such as solar energy and wind energy to produce hydrogen.It has the advantages of high conversion efficiency and high purity of H₂preparation,therefore,it is bound to play an irreplaceable role in the development of hydrogen production technology.The electrochemical water splitting consists of two half-reactions,hydrogen evolution reaction?HER?at the cathode and oxygen evolution reaction?OER?at the anode.At present,precious metals such as Pt-based and Ir O₂/Ru O₂ are considered as excellent catalysts for HER and OER.While,their large-scale application is blocked by their scarcity and high cost.The synthesis of highly efficient,stable and inexpensive transition metal catalysts,naturally,is the key to accelerating the development of electrolyzed hydrogen production technology.In this work,the preparation of CoNi-based bimetallic compound catalysts and the performance of overall water splitting are studied.The main contents are as follows:?1?CoNi oxyhydroxide nanosheets[CoNi-OOH-30?40?/Ti]are synthesized through two steps and used as efficient bifunctional catalysts in alkaline media.First,a shape-controlled CoNi-X/Ti alloy?X denotes electrodeposition time?with a ridge-like morphology that in-situ deposited on titanium sheets is obtained by electrodeposition.Then,CoNi-30/Ti is further electrooxidized to obtain the CoNi-OOH-30?40?/Ti oxyhydroxide nanosheets,which exhibits good catalytic performance for overall water splitting.It is found that the small overpotentials need to reach?210 and 279m V if CoNi-OOH-30?40?/Ti nanosheets can approach±10 m A cm^?2,the corresponding tafel slopes are 67 and 62 m V/dec,which exhibits good stabilities for HER and OER in alkaline solution,respectively.A water electrolyzer,using CoNi-OOH-30?40?/Ti as anode and cathode catalysts,can reach 10 m A cm^?2 at a voltage of 1.76 V.Due to the combination of CoNi alloy and CoNi oxyhydroxides,CoNi-OOH-30?40?/Ti nanosheets maintains10 m A cm^?2 for at least 60 h in alkaline media with ignorable activity losses.It is believed that the present work provides a facile and feasible strategy to fabricate transition bimetallic oxyhydroxide catalysts with high efficiency and stability in alkaline conditions.?2?An efficient bimetallic telluride?CoNi Te₂/NF?catalyst are synthesized by a two-step method for OER in this part.The physico-chemical characterizations confirm the existence of CoNi Te₂/NF surface which is covered by bimetallic telluride compounds with 3D carnation-like morphology,composing of defective nanosheets and well-distributed on 3D nickel foam?NF?.Notably,the relevant electrochemical characterizations demonstrate that CoNi Te₂/NF catalyst exhibits very low onset potential and overpotential at 10?181 m V?,500?230 m V?and 1000?270 m V?m A cm^?2 with low Tafel slope?44 m V/dec?.Besides,it also exhibits a long-term durability of lasting 24 h at100,500 and 1000 m A cm^?2,respectively,without distinct deactivation.This outstanding improved performance could be due to the strong covalency around the CoNi metal center caused by Te.Futhermore,the unique carnation-like structure provides large electrochemical surface area,allowing the exposure of higher number of active sites for OER.Finally,the self-supported structure,without binders,could also improve the overall performance.This work thus provides a simple and feasible method for the preparation of multi-metal telluride material,which is promising to be uesd as a highly efficient and stable catalyst at large current densities.