Potentiostatic Tests Research Articles

Statistical analysis of the pitting corrosion induced by potentiostatic pulse tests of wrought and SLM 316L stainless steels

An original approach coupling potentiostatic pulse tests and statistical analysis of the pitting features was carried out to compare the sensitivity to pitting corrosion of wrought and SLM 316L SS (stainless steels). The measurement and analysis of current densities during potentiostatic pulse tests has led to a better understanding of the pitting corrosion behavior of wrought and SLM 316L SS in 4 mol.l-1 NaCl solution at 50 °C. The association of global measurements and local observations showed that the two stainless steels exhibit different pitting mechanisms. Moreover, a slightly different susceptibility to pitting corrosion is found between the direction of manufacture and the normal direction for the 316L SLM with these tests. The role of the microstructure and the passive film in the pitting corrosion behavior is discussed.

The performance research of TaC modified 316L bipolar plate for proton exchange membrane fuel cell

The corrosion resistance and conductive property are two crucial factors affecting the performance of bipolar plates in proton exchange membrane fuel cell (PEMFC). In this research, a TaC coating is deposited on a 316L bipolar plate through plasma surface modification technology. The electrochemical property of bare 316L and TaC modified bipolar plate has been studied in a simulated PEMFC operation environment. The electrochemical analysis indicates that the performance of bipolar plate has been significantly improved due to the effective effect of TaC modified coating. An obviously decreased corrosion current density is represented by TaC modified bipolar plate and the corrosion potential is more positive in a simulated electrolyte environment. A satisfactory water contact angle of 80.5° is obtained to be beneficial to the water management of PEMFC after surface modification. Furthermore, the TaC-316L bipolar plate presents a minor interfacial contact resistance (ICR) and maintains a favourable result after the potentiostatic polarization test.

Assessment of Corrosion in Offshore R.C. Piers and Use of Microsilica to Reduce Corrosion Induced oxidation (A Case Study of Wharves 11 and 12 in Imam Khomeini Port-IRAN)

reinforced concrete structures in these are as exposed to chloride aggressive marine environments. Therefore, it is important to provide protection and offer appropriate repair methods of buildings vulnerable to the degrading effects of corrosion. The present study sets out to identify and evaluate the causes and extent of corrosion observed in piers Imam Khomeini port. The microsilica is used to reduce corrosion. In order to achieve the above-mentioned goals, a number of experimental field tests were performed to determine the level of concrete condition in terms of reinforcement corrosion. Some tests were conducted to determine the conditions concrete piers in terms of reinforcement corrosion. Then a reinforcement corrosion density test is performed by using Potentiostat test involving a placement process; with different water-to-cement ratios and superplasticizers, the microsilica content was 5%, 10%, and 15%. And microsilica can serve as an alternative to cement and was measured according to ASTM standards. Microsilica was exposed to aggressive conditions at different periods and a concrete compressive strength test was performed. The results show that the compressive strength and corrosion resistance of the concrete increased for concrete mixture containing 10% microsilica with a water-to-cement ratio of 34% and a superplasticizer ratio of 6

A comparative study of corrosion resistance evaluation of bipolar plate materials for proton exchange membrane fuel cell

Reliable assessment of corrosion resistance is critical in seeking the appropriate materials for bipolar plate (BPP) while corrosion of BPP still remains a key challenge in proton exchange membrane fuel cell (PEMFC). In this work, the effects of accelerated and simulated testing conditions as well as potential on corrosion behaviours and microstructure evolutions of stainless steel bipolar plate are studied with SS316L by potentiodynamic and potentiostatic tests, and electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Moreover, the rationalities of evaluating corrosion resistance of materials for BPP under accelerated and simulated testing conditions with different potentials are analyzed based on electrochemical tests and corrosion mechanisms of SS316L. The results reveal that pitting is the main corrosion mechanism for SS316L in the simulated or real PEMFC working conditions. However, the dominant corrosion mechanisms are changed to intergranular and uniform corrosion at the potentials of 1.15 V–1.55 V (vs. SHE), respectively, when tests are performed in accelerated conditions with pH = 0.3. The results indicate that the accelerated conditions may be inappropriate for evaluating corrosion resistance of materials for BPP, especially at higher potentials. • Rationality of evaluating corrosion resistance under different testing conditions are discussed. • The performance of SS316L under different testing conditions are investigated. • The corrosion mechanism of SS316L under different testing conditions are revealed. • Accelerated conditions may be inappropriate for evaluating corrosion resistance of bipolar plate. • High potentials need to be considered to evaluate corrosion resistance of bipolar plate materials.

Study of wear and corrosion behavior of cathodic plasma electrolytic deposition of zirconia– hydroxyapatite on titanium and 316L stainless steel in Ringer’s solution

Abstract The wear resistance and corrosion behavior of titanium and 316L stainless steel were studied after depositing a composite coating of zirconia and hydroxyapatite using the cathodic plasma electrolytic deposition technique. No sign of adhesive wear was observed on coated samples due to the unique surface morphology of the treated samples, after a pin on disk wear test in Ringer’s solution. The average values of friction coefficient for treated titanium and steel samples were observed to be 0.2 which exhibited a decrease of about 4 fold for titanium and 7 fold for steel with respect to the substrates. As a result of potentiostatic cyclic tests in Ringer’s solution the corrosion current density of coated steel (2.47 × 10–10 A cm–2) was found to be much lower than for the steel substrate (1.87 × 10–7 A cm–2), treated and untreated Ti (6.60 × 10–6, 4.17 × 10–7 A cm–2), indicated the increase in corrosion resistance of steel and decrease of it for titanium after coating.

Is the Degradation of Fe-N-C Catalysts in Proton Exchange Fuel Cells Caused By Hydrogen Peroxide Formation?

In fuel cells chemical energy is directly converted into electricity. Based on this, fuel cells are attractive for automotive propulsion. However, a major drawback that hinders the widespread use of fuel cells are the costs. A major cost contributor in today’s state of the art fuel cells is the catalyst; namely platinum and its alloys that are used to catalyse the hydrogen oxidation reaction and the oxygen reduction reaction (ORR) [1]. Most of the expensive metal is required for the cathodic ORR. However, Fe-N-C catalysts are a potential alternative to Pt/C as they reach promising activity while the stability still needs to be improved. There seems to be a trade-off between activity and stability for this kind of catalysts. Beside other causes of degradation, it is discussed that hydrogen peroxide formation is one of the driving forces [2]. While molecular FeN4 centres are assumed to reduce oxygen to water, other phases are suggested to contribute to hydrogen peroxide formation. Such side phases are e.g. iron or iron carbide which are found in the catalysts after high temperature pyrolysis or if insufficient acid leaching was applied [3].However, there is no systematic study if under fuel cell conditions indeed hydrogen peroxide formation from these side phases is at the origin of instability or maybe the leaching of iron species (from these side phases) with subsequently induced Fenton’s reaction might cause the degradation. The knowledge on this is required for future catalyst design and therefore given attention in this work.In order to address this point, small quantities of an FeNC catalyst were post-modified with different metals as e.g. Pt, Pd, Ag in order to tune the selectivity for hydrogen peroxide formation of the resulting catalyst while still keeping the iron-related composition the same.The catalysts were characterized by cyclic voltammetry and rotating ring disc electrode experiments in order to see to what extent specific adsorption occurs and to determine the ORR activity and selectivity in aqueous electrolyte (0.1M H2SO4).Besides, polarization curves were measured in H2/O2 fuel cells and potentiostatic stability tests (12h) were performed at U = 0.6 V to identify activity and stability under operating conditions.We will discuss to what extent hydrogen peroxide formation correlates with the degradation of FeNC catalysts in proton exchange fuel cells.

Microstructural evolution and corrosion behavior of Ti–6Al–4V alloy fabricated by laser metal deposition for dental applications

In this study, microstructural evolution and corrosion behavior of Ti–6Al–4V (TC4) alloy fabricated by laser metal deposition (LMD) were investigated in simulated saliva at 37 °C as a function of scanning strategies. One-way scanning possessed a higher corrosion resistance than cross-scanning, but both of those were inferior to the wrought one. Compared with conventional wrought counterpart, the higher content of β phase improved the corrosion resistance. Results of Mott–Schottky and potentiostatic tests indicated that the passive film upon the surfaces of all the samples exhibited an N-type semiconductor structure and instantaneous nucleation. Of these, the LMD-ed parts displayed a lower donor concentration, higher vacancy diffusion coefficient, and thicker passive film than the wrought samples. XPS analysis revealed that the double-layer structure of passive film leads to a dense protective layer on the surface while the oxide contents of the three were different.

Properties of C-doped CrTiN films on the 316L stainless steel bipolar plate for PEMFC

C doped CrTiN films were deposited on 316L stainless steel by magnetron sputtering technology to investigate corrosion resistance and electrical conductivity. The sputtering current of the C target alter to obtain various C contents. The carbon target currents are 0 A, 3 A and 6 A, respectively. The result of SEM confirms that deposited films have a dense and uniform microstructure. CrTiN coating consist of Cr, CrN and TiN phases. With the increase of C carbon target currents, Cr crystal structure vanishes, and the amorphous carbon and carbides appear. The result of the potentiodynamic polarization test in the simulate PEMFC environment reveals that C doped CrTiN coating can improve samples’ corrosion resistance. At 1.1 V (vs. SHE) potentiostatic tests, the C-6A has the lowest current density, 6.09 × 10−7 A/cm2. Interfacial contact resistance decreases with the addition of C atoms. The C-6A coated sample has the lowest interfacial contact resistance values, 5.5 mΩ cm2.

Chemical Stability and CO2 Electrolysis Performance of La0.3Sr0.7Fe0.7Cr0.3O3- δ in CO2/CO Environments

LMFCr (M = Sr, Ca) has emerged as a highly promising class of perovskite oxide materials for use as symmetrical electrodes in reversible solid oxide fuel cells (RSOFCs).1 While there are numerous studies on the efficacy of these materials as symmetrical electrodes for SOFCs,1-5 a detailed study on their chemical stability and electrochemical performance as fuel electrodes in CO2/CO environments has not yet been reported. This work aims to address the stability of the Sr analogue of LMFCr, namely, La0.3Sr0.7Fe0.7CrO3-δ (LSFCr), in low pO2 environments consisting of CO2/CO gas mixtures (10-11-10-18 atm) to establish the range of pO2 over which the electrode material is structurally and electrochemically stable. This is relevant under CO2 reduction conditions as the stability limit will define the allowable CO2 utilization in these cells in practice.The chemical and phase stability was studied on LSFCr powders and pellets via XRD, TGA, and SEM in different pO2 atmospheres ranging from pure CO2, CO (balance N2), and 90-70% CO2:10-30% CO containing mixtures. Powdered LSFCr remains structurally stable in 20-100% CO2 (balance N2, pO2 = 10-11 – 10-12 atm) from room temperature to 800 oC without any decomposition. On the other extreme, a reversible decomposition occurs at 800 oC in 30% CO (balance N2, pO2 ~ 10-26 atm) resulting in the formation of a Ruddlesden-Popper phase, Fe nanoparticles (NPs), and some carbon fibers, originating from the Fe NPs. However, this decomposition can be reversed by heat treatment in air at 800 oC. While no evidence for coke formation is obtained in 90-70% CO2:10-30% CO (pO2 = 10-17 – 10-18 atm) mixtures at 800 oC, in 70CO2:30CO, minor impurities of SrCO3 and Fe NPs are observed, with the latter potentially being beneficial to the electrochemical activity of the perovskite.Electrochemical characterization was carried out on symmetrical cells prepared by printing ~25 µm single phase LSFCr electrode layers, with an area of ca. 0.5 cm2, on both sides of a 1” diameter SDC buffered YSZ electrolyte, followed by painting on Au paste as the current collectors. The cells were mounted in an open flanges cell testing setup (Fiaxell, Switzerland) and supplied with 50 mL/min air at the oxygen electrode and 50 mL/min CO2:CO mixtures at the fuel electrode. The performance of full cells was determined in various CO2:CO ratios (Pure CO2, 90:10, and 70:30) at 800 oC via electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry. Consistent with prior work, symmetrical 2-electrode full cells showed very good electrochemical performance at 800 oC, both in the SOFC and SOEC modes. Furthermore, LSFCr full cells exhibited excellent short-term stability in 15-min potentiostatic stability tests at 1.2-1.5 V, while medium-term potentiostatic tests at 1.1 and 1.2 V showed that LSFCr exhibits exceptional stability during CO2 electrolysis in all gas atmospheres over several 100 hours, with the oxygen electrode facilitating the oxygen evolution reaction (OER) at the same time. These results suggest that LSFCr has the potential to be a very efficient and stable electrode material for symmetrical SOC applications. References (1) Chen, M.; Paulson, S.; Thangadurai, V.; Birss, V. Journal of Power Sources 2013, 236, 68-79.(2) Chen, M.; Paulson, S.; Thangadurai, V.; Birss, V. ECS Transactions 2012, 45, 343-348.(3) Chen, M.; Paulson, S.; Kan, W. H.; Thangadurai, V.; Birss, V. Journal of Materials Chemistry A 2015, 3, 22614-22626.(4) Molero-Sanchez, B.; Addo, P.; Buyukaksoy, A.; Paulson, S.; Birss, V. Faraday Discussions 2015, 182, 159-175.(5) Addo, P. K.; Molero-Sanchez, B.; Chen, M.; Paulson, S.; Birss, V. Fuel Cells 2015, 15, 689-696.

A new experimental method to simulate dynamic crevice corrosion in modular hip arthroplasty

A new method was developed to study the complex corrosion mechanism found in modular hip arthroplasty, i.e., dynamic crevice corrosion. Short wear events followed by rest times were applied in a conformal tribocontact to simulate different activity levels. Likewise, stepped potentiostatic polarization testing and electron microscopy were used to compare dynamic (continuous and interrupted) and static conditions. Results showed that 316L stainless steel underwent severe corrosion under the dynamic setting. The findings reproduced the extent and morphology of attack found in a retrieved implant. Thus, the new method could be used to investigate the corrosion susceptibility of modular hip arthroplasty.

Evaluation of the Possibility of Using 1.4462 and 1.4501 Steel as a Construction Material for Apparatus Operating at an Increased Temperature and with Corrosive Factors.

The objective of this study was to determine the requirements for steels used as construction materials for chemical apparatus operating at an elevated temperature and to correlate them with the properties of the tested steels. The experimental part examined the influence of the annealing process on the structure and properties of X2CrNiMoN22-5-3 (1.4462) and X2CrNiMoCuWN25-7-4 (1.4501) steel. Heat treatment was carried out on the tested samples at a temperature of 600 °C and 800 °C. Changes were observed after the indicated time intervals of 250 and 500 h. In order to determine the differences between the initial state and after individual annealing stages, metallographic specimens were performed, the structure was analyzed using an optical microscope and the micro-hardness was measured using the Vickers method. Potentiostatic tests of the samples were carried out to assess the influence of thermal process parameters on the electrochemical properties of the passive layer. An increase in the hardness of the samples was observed with increasing temperature and annealing time, the disappearance of magnetic properties for both samples after annealing at the temperature of 800 °C, as well as a significant deterioration in corrosion resistance in the case of treatment at a higher temperature.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Influence of the substrate pre-treatment on the mechanical and corrosion response of multilayer DLC coatings

This work evaluates the mechanical, tribological and corrosion response of single-layer and multilayer DLC films deposited on top of martensitic stainless steel, which was previously plasma nitrided. The efficiency of plasma nitriding as pre-treatment was evaluated using a control group of samples, which was only coated under the same conditions. The pre-treated samples showed a better adhesion of both single and multi-layer DLC films, showing no signs of spallation after applying up to 50 N load during the scratch test.Fretting wear tests (ball on disk) with applied loads 40‐70 N were used to evaluate the mechanical response of the different systems. The best response to fretting wear was given by the coatings deposited onto the pre-treated stainless steel substrate, showing a good mechanical stability without cracking up to 70 N load. Additionally, the corrosion resistance evaluated using step-increasing bias potentiostatic tests, turned out to be acceptable when using plasma nitriding as a pre-treatment. On the contrary, the DLC coatings on top of non- pre-treated substrates failed at a potential 400 mV lower than the 1DLC or 5DLC + N samples. Finally, it is seen that combining nitriding with DLC in the form of multilayers constituted the best protective system, since it can delay the formation of pathways between the corrosive solution and the substrate, until 2000 V bias and 3 hours duration of the experiment.

LOCALISED CORROSION OF STAINLESS STEELS 316L AND 2205 IN SYNTHETIC BENTONITE PORE WATER AND BENTONITE SLURRY

One concept for Czech canister construction for deep geological repository considers stainless steel as an inner case material. Corrosion resistance to localised (pitting/crevice) corrosion and stress corrosion cracking of austenitic stainless steel 316L and duplex steel 2205 was studied. The environment was synthetic bentonite pore water (SBPOW) of domestic bentonite BaM, or a slurry of bentonite in SBPOW. Tests were carried out between 40 °C and 90 °C under anaerobic conditions of a nitrogen atmosphere. The following methods were used for evaluation: potentiostatic tests at oxidation-reduction potential of the environment, long-term exposure tests in SBPOW and slurry, slow strain rate tensile test (SSRT), exposure test of U-bends, and optical microscopy. Results showed no susceptibility of either material to stress corrosion cracking. No localised corrosion was observed up to 70 °C. There was no localised attack observed in SBPOW at 90 °C, but there was localised corrosion detected in the bentonite slurry. Forced breakdown of the passive layer during SSRT, and artificial crevices (O-rings), showed no effect on localised corrosion propagation. The detrimental effect was probably a result of the adsorption ability of the bentonite particles, which allowed breakdown of passive layer and disabled repassivation of metastable pits.

Ampoule method fabricated sulfur vacancy-rich N-doped ZnS electrodes for ammonia production in alkaline media

The electrochemical production of green and low-cost ammonia requests the development of high-performance electrocatalysts. In this work, the ampoule method was applied to modulate the surface of the zinc electrode by implanting defects and low-valent active sites. The N-doped ZnS electrocatalyst was thus generated by sulfurization with thiourea and applied for electrocatalytic nitrogen reduction reaction (ENRR). Given the rich sulfur vacancies and abundant Zn-N active sites on the surface, excellent catalytic activity and selectivity were obtained, with an NH3 yield rate of 2.42 × 10–10 mol s−1 cm−2 and a Faradaic efficiency of 7.92% at − 0.6 V vs. RHE in 0.1 M KOH solution. Moreover, the as-synthesized zinc electrode exhibits high stability after five recycling tests and a 24 h potentiostatic test. The comparison with Zn foil, non-doping ZnS/Zn and recent metal sulfide electrocatalysts further demonstrated advanced catalytic performance of N@ZnS/Zn for ENRR. By simple synthesis, S vacancies, and N-doping defects, this promising electrocatalyst would represent a good addition to the arena of transition-metal-based catalysts with superior performance in ENRR.Graphic abstract

Fretting-corrosion in hip taper modular junctions: The influence of topography and pH levels – An in-vitro study

Contemporary hip implants feature a modular design. Increased reported failure rates associated with the utilization of modular junctions have raised many clinical concerns. Typically, these modular interfaces contain circumferential machining marks (threads or microgrooves), but the effect of the machining marks on the fretting-corrosion behavior of total hip implant materials is unknown. This study reports the effects of microgrooves on the fretting-corrosion behavior of hip implant materials. The flat portions of two cylindrical, polished, CrCrMo alloy pins were loaded horizontally against one rectangular Ti alloy rod. Two surface preparation groups were used for the Ti6Al4V rod (polished and machined). The polished group was prepared using the same methods as the CoCrMo pins. The machined samples were prepared by creating parallel lines on the rod surfaces to represent microgrooves present on the stem tapers of head-neck modular junctions. Newborn calf serum (30 g/L protein content; 37 °C) at pH of levels of 7.6 and 3.0 were used to simulate the normal joint fluid and a lowered pH within a crevice, respectively. The samples were tested in a fretting corrosion apparatus under a 200N normal force and a 1Hz sinusoidal fretting motion with a displacement amplitude of 25 μm. All electrochemical measurements were performed with a potentiostat in a three-electrode configuration.The results show significant differences between machined samples and polished samples in both electrochemical and mechanical responses. In all cases, the magnitude of the drop in potential was greater in the machined group compared to the polished group. The machined group showed a lower total dissipated friction energy for the entire test compared to the polished group. Additionally, the potentiostatic test measurements revealed a higher evolved charge in the machined group compared to the polished group at both pH conditions (pH 7.6 and 3.0). The machined surfaces lowered the overall dissipated friction energy at pH 7.6 compared to pH 3.0, but also compromised electrochemical performance in the tested conditions. Therefore, the role of synergistic interaction of wear and corrosion with surface topographical changes is evident from the outcome of the study. Despite the shift towards higher electrochemical destabilization in the machined group, both polished and machined groups still exhibited a mechanically dominated degradation.

Surface Enhanced Raman Spectroscopy With Electrodeposited Copper Ultramicro-Wires With/Without Silver Nanostars Decoration.

The electrochemical preparation of arrays of copper ultramicrowires (CuUWs) by using porous membranes as templates is critically revisited, with the goal of obtaining cheap but efficient substrates for surface enhanced Raman spectroscopy (SERS). The role of the materials used for the electrodeposition is examined, comparing membranes of anodized aluminum oxide (AAO) vs. track-etched polycarbonate (PC) as well as copper vs. glassy carbon (GC) as electrode material. A voltammetric study performed on bare electrodes and potentiostatic tests on membrane coated electrodes allowed the optimization of the deposition parameters. The final arrays of CuUWs were obtained by chemical etching of the template, with NaOH for AAO and CH2Cl2 for PC. After total etching of the template, SERS spectra were recorded on CuUWs using benzenethiol as SERS probe with known spectral features. The CuUW substrates displayed good SERS properties, providing enhancement factor in the 103–104 range. Finally, it was demonstrated that higher Raman enhancement can be achieved when CuUWs are decorated with silver nanostars, supporting the formation of SERS active hot-spots at the bimetallic interface.

A comparative study on the critical pitting criteria of a super ferritic stainless steel at different temperatures in chloride or bromide solution

Critical pitting criteria of S44660 are investigated in chloride or bromide solution. The more aggressive Cl− does not lead to lower Eb values in all temperature ranges. The Eb-T curves reveal that the pitting behavior with temperature can be divided into transpassivation, transition, and pitting region. The transition region, in which pitting is induced by transpassivation, is verified by potentiostatic tests. The much wider transition region in bromide solution is attributed to the weakened repassivation ability caused by the interaction between Br− and Mo, which indicates that pitting is more prone to occur in bromide solution at a lower temperature.

Fabrication and properties evaluation of novel Fe46-XCr23Mo14Co7PXB5Si5 (X=0, 6) m metallic glasses deposited by DC magnetron sputtering

Novel Fe46Cr23Mo14Co7B5Si5 and Fe40Cr23Mo14Co7P6B5Si5 thin film metallic glasses (TFMGs) were successfully deposited using direct current magnetron sputtering process. Different microstructural evaluations were carried out including XRD, FE-SEM, EPMA, AFM, and TEM-SAED. Mechanical properties such as nano-indentation and fracture toughness tests were also performed on different substrates and under various applied forces. In addition, corrosion performance was carried out by potentiodynamic polarization, potentiostatic and electrochemical impedance spectroscopy tests. Formation of full, glassy phase was confirmed by XRD as well as TEM-SAED for both films. It was found that adding P element changed the cross-sectional growth of TFMG, decreased surface roughness and improved mechanical properties. It was also shown that the substrate type had minor influence on the fracture toughness values of TFMGs as compared to the applied force. P addition also led in an excellent corrosion resistance and significantly increase in polarization resistance, with more than 400 times as compared to the one for SS304 substrate.

Copper-indium hybrid derived from indium-based metal-organic frameworks grown on oxidized copper foils promotes the efficient electroreduction of CO2 to CO

This work reports a novel and effective method for the preparation of the copper-indium bimetallic electrocatalysts by the in situ growth of indium-based metal organic frameworks on oxidized copper foils as the precursor. Compared with the oxide-derived copper and the copper-based carbon material derivative grown in situ on oxidized copper foils, the as-prepared copper-indium electrocatalyst with a self-supporting structure, high roughness factor and rich lattice defects exhibits a superior CO Faradaic efficiency of 95% and good stability for the 36-h potentiostatic test at −0.6 V versus a reversible hydrogen electrode. Density functional theory calculations indicated that the indium atoms occupying the surface copper vacancy defects show lower free energy needed for the formation of *COOH and more difficult desorption of *H than indium atoms, supported on the perfect copper surface. Thereby, the copper-indium catalyst promotes CO2 electroreduction to CO and strongly inhibits hydrogen evolution.