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
Electrocatalytic Water splitting step terrace 1.4 1.4 12 C -S atom site S(001) 1.0 Ni atom site 20 4.92 456 0,U=0V Bond site OOH 0.8 -Ring site Ni(001) 2.98 0.6 NiS(210) b200i) 0 S2(210) b4210) 0.4 R(210) 1.17 087 0.2 OH 0.52n 0 H'+e ⅓H -0.06 =1.23W 0.0 0.0 *+2H,0 02 -0.64 -0.64 02 -0.87 Reaction coordinate -2.32U=1.81V (210)surface (0.58) HER Mi111) ● 000m 0.91 OER 0.90 Ni/CeO-(111) 0.5 0.13 0 Ni4Ce0(111) Cu surface: 0.5 Ca02.(111) 1 H,O TS H+HO
Theoretical Calculations HER OER Electrocatalytic Water splitting
HER on NiS/NiSnS Hydrogen energy though hydrogen evolution reaction(HER)is regarded as a desirable substitute for non-renewable fossil fuels; 3d transition metal sulphides present higher catalytic efficiency due to enhancement of conductivity and number of electrochemically active surface sites. >Collaborations with the Institute for 50 Clean Energy Advanced Materials at -PC -Ni,S,Ni,Sn,S-ii N5/NF 100 -Ni,5 Ni,5n,S-i NS/NF -Ni,5 Ni,5m,5-ii NS/NF Southwest University,Chongqing; -NiS,NS/NE .150 -Nifo单 The Ni,Sn2S,/NiS,>porous nanosheets 0.6 -0.4 -0.2 0.0 02 0.4 Potential (V vs.RHE) -inital contain the characteristic of NiS,and Interface (wo vu) -after 20 hours Ni,Sn2S2 phases: -50 The NisSn2S2/NigS2 Shows a very low overpotential and a long-time stability -100 -0.8-0.6-0.4-0.20.0 for HER activity. Potential (V ys.RHE)
The catalytic activity of Ni3S2 and Ni2Sn3S2 toward hydrogen evolution reaction Hydrogen energy though hydrogen evolution reaction (HER) is regarded as a desirable substitute for non-renewable fossil fuels ; 3d transition metal sulphides present higher catalytic efficiency due to enhancement of conductivity and number of electrochemically active surface sites. ➢ Collaborations with the Institute for Clean Energy & Advanced Materials at Southwest University, Chongqing; ➢ The Ni3Sn2S2 /Ni3S2 porous nanosheets contain the characteristic of Ni3S2 and Ni3Sn2S2 phases; ➢ The Ni3Sn2S2 /Ni3S2 shows a very low overpotential and a long-time stability for HER activity. HER on NiS/NiSnS
HER on NiS/NiSnS 30 NiS2(101)-S NiaS2(101)-Ni 20 量-(101)S Ni3S2(101)-Ni2 10 ◆(101-N3 Ni,S,(101)-Ni3 101-N2 -(101)1 4-(012-NSr ◆-(012外-S1 ◆-012分5 ●-(012外2 NiSn2S2(012)-Ni/Sn NiSn2S2(012)-S1 L .8 -6 4 2 NigSn2S2(012)-Ni Ni3Sn2S2(012)-S2 Sulfur Chemical Potential/eV NigS2(101)-Ni3 and NiSn2S2(012)-Ni/Sn is more stable under the O-rich condition;NiS2(101)-S and NiSn2S2(012)-S2 is stable under the S-rich condition
The catalytic activity of Ni3S2 and Ni2Sn3S2 toward hydrogen evolution reaction Ni3S2 (101)-Ni3 and Ni3Sn2S2 (012)-Ni/Sn is more stable under the O-rich condition; Ni3S2 (101)-S and Ni3Sn2S2 (012)-S2 is stable under the S-rich condition. Ni3S2 (101)-S Ni3S2 Ni3S2 (101)-Ni2 (101)-Ni3 Ni3S2 (101)-Ni1 Ni3Sn2S2 (012)-Ni/Sn Ni3Sn2S2 (012)-S1 Ni3Sn2S2 (012)-Ni Ni3Sn2S2 (012)-S2 HER on NiS/NiSnS
HER on NiS/NiSnS △GH*)=AEH*)+△ZPE-TAS AE(H*)is the binding energy,AZPE is zero point energy change of H*,and TAS is entropy change of H*. Surface Ad.sites E(H*)/eV ZPE(H*)/ ZPE/eV G(H*)/eV eV Ni3S2(101)-Ni3 Nil 0.452 0.323 0.127 0.779 Ni2 0.468 0.346 0.150 0.819 S-Ni 0.365 0.428 0.232 0.797 Ni3Sn2S2(012)-Ni/Sn Ni -0.363 0.323 0.127 -0.036 Sn-Ni -0.363 0.323 0.1279 -0.035 NiS(101)-S Ni -0.741 0.442 0.246 -0.295 Ni-S 0.449 0.380 0.184 0.834 Ni3Sn2S2(012)S2 Sn/Ni -2.768 0.323 0.127 -2.441
Surface Ad. sites E(H*)/eV ZPE(H*)/ eV ZPE/eV G(H*)/eV Ni3S2(101)-Ni3 Ni1 0.452 0.323 0.127 0.779 Ni2 0.468 0.346 0.150 0.819 S-Ni 0.365 0.428 0.232 0.797 Ni3Sn2S2(012)-Ni/Sn Ni -0.363 0.323 0.127 -0.036 Sn-Ni -0.363 0.323 0.1279 -0.035 Ni3S2(101)-S Ni -0.741 0.442 0.246 -0.295 Ni-S 0.449 0.380 0.184 0.834 Ni3Sn2S2(012)-S2 Sn/Ni -2.768 0.323 0.127 -2.441 ∆G(H*) =∆E(H*)+∆ZPE-T∆S ∆E(H*) is the binding energy, ∆ZPE is zero point energy change of H*, and T∆S is entropy change of H*. The catalytic activity of Ni3S2 and Ni2Sn3S2 toward hydrogen evolution reaction HER on NiS/NiSnS
HER on NiS/NiSnS (a) (c) 6 -Ni-bulk Ni site V35, 8 -H ---S-bulk 61 S site Ni,S,(101)-Ni CoS Nia on NiS2(101)-Nil: 3S+2Ni Nig on NiS2(101)-Nil: 4S+3Ni NiSn2S2(012)-NiSn 2 10 Energy(eV) ---Ni-bulk Ni sited Sn -H ---Sn-bulk Sn site Sn 2 Ni on NigSn2S2(012)-NiSn: 1s3州 0 Ni,Sn,S,(012)-S2 -6 2 0 Energy(eV)
The catalytic activity of Ni3S2 and Ni2Sn3S2 toward hydrogen evolution reaction (a) Ni3S2 (101)-Ni1 (c) Ni3Sn2S2 (012)-NiSn (b) Ni3S2 (101)-Ni1 (d) Ni3Sn2S2 (012)-NiSn NiA on Ni3S2 (101)-Ni1: 3S+2Ni NiB on Ni3S2 (101)-Ni1: 4S+3Ni (a) Ni3S2 (101)-Ni1 (c) Ni3Sn2S2 (012)-NiSn (b) Ni3S2 (101)-Ni1 (d) Ni3Sn2S2 (012)-NiSn NiA on Ni3Sn2S2 (012)-NiSn: 1S+4Sn+2Ni HER on NiS/NiSnS
