Doping And In-situ Reduction Of LaCoO₃ And Their Electrocatalytic Properties

A series of LaCo_1-xPt_xO_3-?(x=0,0.02,0.04,0.06,0.08)perovskite nano powders were prepared by sol-gel method.The performance of OER(oxygen evolution reaction),HER(hydrogen evolution reaction)and overall water splitting were measured by adjusting the doping amount of Pt element.The samples with the best electrochemical performance in LaCo_1-xPt_xO_3-?perovskite catalysts were treated by in situ hydrogen reduction.The performance of OER,HER and overall water splitting of the Pt/LaCo_0.94Pt_yO_3-?perovskite catalyst was studied.The electrochemical measurements of a series of perovskite catalysts LaCo_1-xPt_xO_3-?(x=0,0.02,0.04,0.06,0.08)showed that the OER and HER performance of perovskite catalysts were improved by doping minor precious metal Pt at B site.Among them,the OER and HER activities of LaCo_0.94Pt_0.06O_3-?perovskite catalysts were the best.The improvement of perovskite catalysts performance after doping minor Pt may be attributed to the following reasons:the electrochemical specific surface area of perovskite catalysts increases,the charge transfer resistance decreases,the charge transfer rate increases,the percentage of surface high oxide species O₂^2-/O^-increases.The main reason is the e_g orbital electrons of Co ion gradually tends to 1.2,and the number of e_g orbital electrons of LaCo_0.94Pt_0.06O_3-?perovskite catalyst is closest to 1.2.These factors make LaCo_0.94Pt_0.06O_3-?perovskite catalyst achieve the best electrocatalysis performance.The electrochemical performance of Pt/LaCo_0.94Pt_yO_3-?perovskite catalyst was studied and the results show that the performance of OER,HER and overall water splitting of Pt/LaCo_0.94Pt_yO_3-?perovskite catalyst have been improved by in-situ hydrogen reduction.The initial potential,overpotential and Tafel slope have been reduced.The potential for overall water splitting is 1.78 V,and the stability test results are good.It is found that the electrochemical specific surface area increases,the charge transfer resistance decreases and the charge transfer rate increases after in-situ hydrogen reduction.The main change is that some Pt ions in the lattice of perovskite catalyst are reduced to Pt and adhere to the surface of the catalyst.The perovskite matrix has a certain space-limited effect on the Pt element obtained by in-situ reduction attached to the catalyst surface,and there is some synergistic effect between the Pt element and the perovskite matrix.Both of them promote the electronic exchange between the Pt element and the perovskite catalyst matrix and the perovskite catalyst matrix itself,thus enhancing the electrocatalysis performance of Pt/LaCo_0.94Pt_yO_3-?perovskite catalyst.This work shows that in-situ reduction can be used as an effective mean to regulate the electrocatalysis activity of perovskite materials.