Catalyst Design for the Electrochemical CO 2 Conversion Peter - PowerPoint PPT Presentation

6 th SCCER Symposium (HaE) Martigny – 25/10/2017 Catalyst Design for the Electrochemical CO 2 Conversion Peter Broekmann Department of Chemistry and Biochemistry University of Bern, Switzerland

6 th SCCER Symposium (HaE) Martigny – 25/10/2017 Outline of the talk  Motivation and introduction  SCCER HaE Storage: WP4  Approach towards catalyst design  Selected examples  Cu foams as catalysts for C2 hydrocarbon formation  Ag foams as catalysts for syn gas and methane production  OD-Cu dendrites as catalysts for alcohol production  Conclusions and outlook

Introduction - Motivation The SCCER Heat and Electricity Storage WP4 WP4 : Catalytic and electrocatalytic CO 2 conversion

Introduction - Motivation * Taget: synthetic fuels and chemical feedstock Alcohols Syn gas Hydrocarbons Formic Acid (MetOH; EtOH; PrOH) (HCO 2 H) (CO/H 2 ) (CH 4 ; C 2 H 4 ) *By courtesey of Günter Schmidt (Siemens)

Introduction - Motivation Target specific catalysts: (i) efficiency (ii) selectivity (iii) durability Syn gas Alcohols Hydrocarbons Formic Acid (MetOH; EtOH; PrOH) (CO/H 2 ) (CH 4 ; C 2 H 4 ) (HCO 2 H)

Introduction - Motivation Approaches towards catalyst design Metal foam catalyst NP-catalysts Cu-foam Cu-NPs Comparison 200µm  ec -CO 2 RR activity  Metal-oxide NPs  Metal dendrites/foams  InO x (C-supported)  Cu, Sn, Ag, Pd  ec -CO 2 RR selectivity  SnO x (C-supported)   OD metal foams Stability  Metal-alloy NPs  Cu/Cu x O  Cu (C-supported)  Sn/SnO x  Cu x Au y (C-supported)  (Ir/IrO 2 )  Cu x Sn y (C-supported)  Supports  Supports  2D Cu mesh  Vulcan  3D Cu skeleton/sponge  rGrOx

Introduction - Motivation Interconnect Materials of Power to gas/liquid technology interest (CO 2 to value) ethylene CO 2 Cu electro-catalyst CO 2 formate Sn electro-catalyst Additive-assisted electrodeposition

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) Metal foam deposition: working principle Plating conditions 1.5 M H 2 SO 4 , 0.2 M CuSO 4 J = -3 A/cm 2 A. Dutta , M. Rahaman, N. C. Luedi, M. Mohos, P. Broekmann , ACS Catal . 6 ( 2016 ) 3804-3814

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) Template/additive controlled deposition of high surface area Cu catalysts (foams) Increasing deposition time 60s 5s 20s 40s 80s 200µm 200µm 200µm 200µm 200µm Plating conditions 1.5 M H 2 SO 4 , 0.2 M CuSO 4 , J = -3 A/cm 2 , Additive package I

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) Product distribution of CO 2 RR on Cu foams Increasing deposition time 60 CO 5s 80s Faradaic efficiency / % C 2 H 4 50 C 2 H 6 Total FE of 40 C 2 products 30 20 10 0 50 100 150 Pore diameter / µ m 200µm 200µm CO 2 electrolysis conditions 1h electroylsis, CO 2 sat. 0.5 M NaHCO 3 E = -0.8 V vs RHE A. Dutta , M. Rahaman, N. C. Luedi, M. Mohos, P. Broekmann , ACS Catal . 6 ( 2016 ) 3804-3814

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) Cu supports for CO 2 RR catalysts 2 mm 2 mm 2D Cu mesh Cu 3D skeleton  Replace the wafer substrate by 3D Cu skeletons and 2D Cu meshes .  Translate the Cu foam catalysts to more realistic supports suitable for gas flow approaches.

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) 2D Cu mesh support 3D Cu skeleton support Increasing deposition time Increasing deposition time  Transfer of the functional Cu foam on the 2D Cu mesh.  Activity towards C2-product formation

Cu foams as catalysts for ec-CO 2 RR (hydrocarbons) 3D Cu skeleton support Product analysis 14 18 C 2 H C 2 H 6 4 12 16 Faradaic Efficiency (%) Faradaic Efficiency (%) 14 10 12 8 10 6 8 6 4 4 2 2 0 0 -1.0 -0.9 -0.8 -0.7 -0.6 -1.0 -0.9 -0.8 -0.7 -0.6 E / V vs. RHE E / V vs. RHE 2D Cu mesh (electroplolished) 2D Cu mesh (electroplolished) 20s deposition of Cu foam on 3D Cu skeleton 20s deposition of Cu foam on 3D Cu skeleton  Presence of well-defined facets on the Cu foam.  Important for C-C coupling reations.

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) Additive-assisted metal foam deposition Primary porosity Secondary porosity (side-walls) (liquid/solid interface) (gas/solid interface) Ag (20s) Ag (20s) Ag (20s) 25µm 50 µm 1 µm Ag (20s) Ag (20s) Ag (20s) 2 µm 200 nm 5 µm

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Product selectivity (liquid/solid interface) Ag (20s) 100 80 FE Ag foams-20s / % CO 60 H 2 CH 4 40 50 µm C 2 H 4 20 Ag (20s) 0 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 E / V vs. RHE CO 2 electrolysis conditions 1h electroylsis, CO 2 sat. 0.5 M NaHCO 3

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Product selectivity (liquid/solid interface) Ag (20s) 100 80 FE Ag foams-20s / % CO 60 H 2 CH 4 40 50 µm C 2 H 4 20 Ag (20s) 0 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 -0.4 E / V vs. RHE  First ec-CO 2 RR catalyst beyond Cu suitable for hydrocarbon formation. 5 µm  Morphology matters!!!

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Product selectivity (liquid/solid interface) 60 Ag (20s) Total Hydrocarbon (CH 4 + C 2 H 4 ) 50 FE / % 40 30 50 µm 20 Ag (20s) 10 0 -1.6 -1.4 -1.2 -1.0 -0.8 -0.6 E / V vs. RHE  First ec-CO 2 RR catalysts beyond Cu for hydrocarbon formation.  Morphology matters!!!

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Catalyst durability (liquid/solid interface) (CO region at -0.8 V vs RHE) -10 Ag (20s) 100 FE H 2 (%) -2 geo / mA cm -8 80 -6 60 Steady state FE CO (%) 50 µm -4 40 FE of H 2 j FE of CO Ag (20s) -2 Steady state current 20 0 0 0 10 20 30 40 50 60 70 Time / hrs 5 µm  Superior stability of the Ag foam catalyst for CO formation.

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Catalyst durability (liquid/solid interface) (CH 4 region at -1.5 V vs RHE) -20 Ag (20s) 100 FE H 2 -30 -2 geo / mA cm 80 -40 FE CO -50 60 Steady state -60 50 µm 40 -70 j FE CH 4 Ag (20s) -80 20 -90 -100 0 0 1 2 3 4 5 6 7 8 9 Time / hrs  Moderate stability of the Ag foam catalyst for CH 4 formation. 5 µm  C1 hydrocarbon pathway is the origin for catalyst degradation.

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) ec -CO 2 RR on Ag foam catalysts Primary porosity Catalyst durability (liquid/solid interface) (CH 4 region at -1.5 V vs RHE) Ag (20s) 120 -0.8 V -0.8 V -0.8 V -0.8 V -0.8 V FE CH 4 100 80 FE CO -1.5 V -1.5 V -1.5 V -1.5 V 60 -1.5 V 50 µm 40 Ag (20s) 20 0 30 60 90 120 150 180 210 240 Time / min. 5 µm  The robust Ag foam catalyst tolerates potential changes.

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) Identical location (IL) HR-SEM inspection ap (20s) ap (20s) ap (20s) as prepared 10 µm 250 nm 100 nm pm (20s) pm (20s) pm (20s) post mortem 4h; -0.8 V vs RHE (CO region) 10 µm 250 nm 100 nm  Ag foam catalst are inherently stable/tolerant against CO formation.  Primary and secondary porosity remains unaffectd by CO production.

Ag foams as catalysts for ec-CO 2 RR (syn gas; CO/H 2 ) Identical location (IL) HR-SEM inspection ap (20s) ap (20s) ap (20s) ap (20s) as prepared 10 µm 100 nm 500 nm 250 nm pm (20s) pm (20s) pm (20s) post mortem 4h; -1.5 V vs RHE (CH 4 region) 10 µm 250 nm 100 nm  Ag foam catalst are inherently unstable/intolerant against CH 4 formation .  Primary porosity remains unaffectd by CO production.

OD-Cu dendrites as catalysts for ec-CO 2 RR (hydrocarbons, alcohols) Functionalization of Cu mesh supports Cu dendrite Cu mesh SEM SEM SEM SEM SEM SEM  Multi-step catalyst preparation  Step 1: electropolishing of the mesh support in phosphoric acid.  Step 2: Potentiostatic electrodeposition of dendritic Cu.  Step 3: Thermal annealing at 300° C for 1h.  Step 4: Reduction of the OD-Cu precursor under ec -CO 2 RR conditions M. Rahaman, A. Dutta , A, Zanetti, P. Broekmann , ACS Catal . ( 2017 ), in press

OD-Cu dendrites as catalysts for ec-CO 2 RR (hydrocarbons, alcohols) Identical location (IL) HR-SEM inspection as deposited (step 2 ) Oxide derived (OD) (step 3 ) (OD) post mortem (step 4 )  The active catalyst forms under operando conditions during ec -CO 2 RR .

OD-Cu dendrites as catalysts for ec-CO 2 RR (hydrocarbons, alcohols) ec -CO 2 RR on OD-Cu dendrites (OD) post mortem (step 4 )  OD-Cu dendrites show superior performance for C2 and C3 alcohol formation .

OD-Cu dendrites as catalysts for ec-CO 2 RR (hydrocarbons, alcohols) ec -CO 2 RR on OD-Cu dendrites Cu mesh Cu dendrite Kortlever et al., Phys. Chem. Lett. 2015, 6, 4073 OD Cu dendrite Nie et al., Angew. Chem. Int. Ed. 2013, 52, 2459-2462