Synthesis Of Noble Metal Based Catalysts And Their Electrocatalytic Performance For Water Splitting In Acidic Medium

Proton exchange membrane water electrolysis（PEMWE）based on acidic medium is considered as a promising technique for hydrogen production due to the immediate response,high purity and high current density.Up to now,the hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）have been mainly catalyzed by precious metal group catalysts in acidic medium.However,low reserves and high cost of precious electrocatalysts seriously hamper the large-scale application in PEMWE.Thus,it is essential to explore efficient and stable HER/OER electrocatalysts with low loading.To this end,this paper mainly carries out the following work:（1）Modulating the electronic structure of support for enhancing hydrogen evolution of Pt nanoclusters.By only changing Pt sources,we successfully designed V_O-rich Pt/TiO₂ and V_O-deficient Pt/TiO₂ catalysts,of which Pt nanoclusters（0.8 nm）anchored on TiO₂ nanosheets with rich and deficient oxygen-vacancy,respectively.ICP-MS and HAADF-STEM results clearly demonstrate that both the sizes and the amounts of Pt loadings are similar in V_O-deficient and V_O-rich Pt/TiO₂.V_O-rich Pt/TiO₂shows a mass activity of 45.28 A·mg_Pt^-1 for HER at-0.1 V vs.RHE in 0.5 M H₂SO₄,which is 16.7 and 58.8 times higher than those of V_O-deficient Pt/TiO₂ and commercial Pt/C,respectively.DFT calculations and In-situ Raman spectra suggest that porous TiO₂with rich oxygen vacancies can simultaneously achieve reversed charge transfer（electrons transfer from TiO₂ to Pt nanoclusters）and enhanced hydrogen spillover from Pt nanoclusters to TiO₂ support,which leads to electron-rich Pt nanoclusters being amenable to proton reduction of absorbed H*,as well as the acceleration of hydrogen desorption at Pt catalytic sites,both promoting the HER.（2）Constructing bimetallic sites for enhanced hydrogen evolution catalysis of Pt nanoclusters.The pyrenyl graphdiyne is firstly wrapped on the sidewalls of carbon nanotubes to form PGDY@CNT hybrid,which is then used as the carbon support to prepare Pt-Co/PGDY@CNT catalyst with bimetallic sites.The electrochemical test results show that the synergistic catalysis between Pt and Co species can remarkably improve the HER performance.In this regard,the Pt-Co/PGDY@CNT can deliver a current density of 10 m A·cm^-2 with an overpotential of 41 m V in 0.5 M H₂SO₄,which is 49 and 325 m V lower than those of Pt/PGDY@CNT and Co/PGDY@CNT.Moreover,the mass activity of Pt-Co/PGDY@CNT catalyst is 8.82 A·mg_Pt^-1 at the overpotential of 100 m V,which is 5.3 and 21.5 times to those of Pt/PGDY@CNT and commercial Pt/C under identical testing conditions.（3）Constructing ruthenium-ruthenium oxide heterointerface for boosting oxygen evolution catalysis in acidic media.Herein,a simple two-step pyrolysis strategy is reported to fabricate 2D Ru-based porous nanosheets with Ru/RuO₂ heterogeneous interface.The optimized RuO₂ NS-475 presents the excellent catalytic performance toward OER with aη₁₀ of 174 m V using standard three-electrode system.In addition,RuO₂ NS-475 remains the activity without significant decay for at least 100 h at 10m A·cm^-2,while commercial RuO₂ displays obviously inferior stability even in 12 h at the same conditions,indicating the improved stability of RuO₂ NS-475.Moreover,we finally assembled a PEMWE electrolyser with RuO₂ NS-475 as anode catalyst to evaluate the practical application potential for water electrolysis.Specifically,the RuO₂NS-475 based electrolyser required only 1.59 and 1.73 V to reach a current density of200 and 500 m A·cm^-2,respectively,far superior to 1.74 and 1.94 V obtained with commercial RuO₂.