Electrocatalysis > Electrocatalysis is a catalytic process involving oxidation or reduction through the direct transfer of electrons. >The electrochemical mechanisms of electrocatalytic processes are important to the development of water oxidation and fuel cells catalysts. 2Ht+2e→2H2(g) >Half the water oxidation reaction is the reduction of protons to hydrogen,the subsequent half reaction. Half-reaction E°(V)÷ H2(g)2H*+2e 三0 H0+2h+→1/202(g)+2H+ O2(g)+4H+4e≥2H20 +1.23
Electrocatalysis Electrochemical Catalysis ➢ Electrocatalysis is a catalytic process involving oxidation or reduction through the direct transfer of electrons. ➢ The electrochemical mechanisms of electrocatalytic processes are important to the development of water oxidation and fuel cells catalysts. ➢ Half the water oxidation reaction is the reduction of protons to hydrogen, the subsequent half reaction. 2H+ + 2e- → 2H2 (g) H2O + 2h+ → 1/2O2 (g) + 2H+
Electrocatalyst ·电催化Electrocatalysis):在电场作用下电极表面 或液相中的修饰物促进或抑制电极上发生的电 子转移反应，而电极表面或溶液相中的修饰物 本身并不发生变化的化学作用 Overall water ectrolys lectroly ·电催化剂的性能具备的特点： 催化剂有一定的电子导电性(conductivity). -高的催化活性(high activity) andem wale -催化剂的电化学稳定性(electrochemical stability) electrolysis water e/ectrolysis 三 。 电催化剂的结构(structure)和组成(composition)、氧化- 三 还原电势(redox potential)、载体(vector)、表面微观结构 Innovative Strategies for Electrocatalytic Water Splitting 和状态(surface microstructures))、溶液中的化学环境 Bo You"(and Yujie Sun" Department of Chemistry and Biochemistry.Utah State University,Logan.Utah B4322.United (chemical solutions))等都会影响其电催化话性。 Acc.Cbem.Res,2018,51(7).pp1571-1590 Cite this:Acc.Chem.Res 20 D01:10.1021ac5acc0unts.8b00002 Ris Citation co
Electrochemical Catalysis 电催化(Electrocatalysis):在电场作用下电极表面 或液相中的修饰物促进或抑制电极上发生的电 子转移反应，而电极表面或溶液相中的修饰物 本身并不发生变化的化学作用. Electrocatalyst • 电催化剂的性能具备的特点： – 催化剂有一定的电子导电性 (conductivity) – 高的催化活性 (high activity) – 催化剂的电化学稳定性 (electrochemical stability) • 电催化剂的结构(structure)和组成(composition)、氧化－ 还原电势(redox potential)、载体(vector)、表面微观结构 和状态(surface microstructures)、溶液中的化学环境 (chemical solutions)等都会影响其电催化活性
Electrocatalytic Water splitting Oxygen Evolution Reaction(OER) Neutral/Acidic medium Alkaline medium M+H,O→M-OH+Ht+e M+OH→M-OH M-OH→M-O+Ht+e M-OH→M-OH+ei 2M-0→02+2M M-OH-+M-OH-M-O++M+H2O+e 2M-0→O,+2M Hydrogen Evolution Reaction (HER) Acidic medium Neutral/Alkaline medium M+HO*+e→MH+HO M+H,O+e→MH+OH MH+H,Ot+e→H,+HO+M MH+HO+e→H2+M+OH 2MH→H2+M 2MH→H2+M
Chemical Reactions Hydrogen Evolution Reaction (HER) Oxygen Evolution Reaction (OER) Acidic medium M + H3O+ + e- → MH + H2O MH + H3O+ + e- → H2 + H2O + M 2MH→ H2 + M Alkaline medium M+OH- → M-OHM-OH-→ M-OH+eM-OH - +M-OH → M-O++M+H2O+e- 2M-O → O2+2M Neutral/Acidic medium M+H2O→M-OH+H+ +eM-OH→M-O+H+ +e- 2M-O→O2 +2M Neutral/Alkaline medium M + H2O +e- → MH + OHMH + H2O + e- → H2 + M + OH- 2MH→ H2 + M Electrocatalytic Water splitting
Electrocatalytic Water splitting Cyclic-voltammetry循环伏安曲线 Tafel slope塔菲尔斜率 Epa负移（即n)或Epa基本不变，而ipa↑ 线性扫描曲线取I0g,用于分析反应机理 -0.5 一Ni wire 墨 Ni@NPC 0.4 a-Ni,S,@NPC 134.5 mV dec -0.3 117.4 mV dec -0.2 -0.1 63.5 mV dec pa 2.02.5 3.03.54.04.5 0.0 2 1 0 EN Log (j/mA cm) Potential-.current电势电流曲线 Time-current时间电流曲线 40 0 30 16 4 20 OER 12 8 10 0 12 HER OER HER -10 NI,S /NF E°=1.23V 16 ◆一PUC ★一NIS/NF 畅 0 ◆-lroc 畅 -2 -0.6 -0.50.4 0.3-0.2-0.1 0.0 1.2 1.31.41.51.6 1.7 0 50 100 150 20 40 Potential (V vs RHE) Potential (V vs RHE) An Time(h)
Epa Cyclic-voltammetry 循环伏安曲线 E pa 负移(即η↓) 或E pa 基本不变，而i pa↑ Potential-current 电势电流曲线 Time-current 时间电流曲线 Experimental Measurements Tafel slope 塔菲尔斜率 线性扫描曲线取log，用于分析反应机理 Electrocatalytic Water splitting
Electrocatalytic Water splitting HER OER △GH*)=△E(H*)+△ZPE-T△S, △GA=EHO*)-E(*)-EH2o+1/2EH2+(△ZPE-T△S)A-eU △GB=E(O*)-E(HO*)+1/2EH2+(△ZPE-T△S9)B-eU Association of H,O and the energy barrier △Gc-E(HOO*)-E(O*)-EH2o+1/2EH2+(△ZPE-T△S)c-eUU △GD=E(*)-E(HOO*)+Eo2+1/2EH2+(△ZPE-T△S)D-eU AE(H)is the binding energy of H atom on adsorption sites 。 AZPE is the zero point energy change of H'by using the equation of AZPE=ZPE(H)- 1/2ZPE(H)with a value of ZPE(H)=0.392 eV. TAS is the entropy change of H',which is determined to be-0.20 eV at 298 K and 1 atm. E(*),E(HO*),E(O*),and E(HOO*)are the computed DFT energies of the pure surface and the adsorbed surfaces with HO*,O*,and HOO*,respectively ·△G(2H0→02+2H2)=4.92eV=E02+2EH2-2EH0+(△ZPE-T△S92H0→O2+2H)
• ΔE(H* ) is the binding energy of H atom on adsorption sites • ΔZPE is the zero point energy change of H* by using the equation of ΔZPE = ZPE(H* ) – 1/2ZPE(H2 ) with a value of ZPE(H2 ) = 0.392 eV. • TΔS is the entropy change of H* , which is determined to be -0.20 eV at 298 K and 1 atm. • E(*), E(HO*), E(O*), and E(HOO*) are the computed DFT energies of the pure surface and the adsorbed surfaces with HO*, O*,and HOO*, respectively • ∆G(2H2O→O2+2H2 ) = 4.92 eV = EO2 + 2EH2 - 2EH2O + (∆ZPE - T∆S)(2H2O→O2+2H2 ) Theoretical Calculations HER OER Electrocatalytic Water splitting Association of H2O and the energy barrier