Solid Polymer Electrolyte Water Electrolysis Research Articles

Stable and high-performance Ir electrocatalyst with boosted utilization efficiency in acidic overall water splitting

The industrialization of solid polymer electrolyte water electrolysis (SPEWE) dominantly relies on electrocatalyst with high stability and efficiency for oxygen evolution reaction (OER) catalysis. In this work, we report a facile method to construct α-Ni(OH)2@Ir core–shell nanoparticles as bifunctional electrocatalyst for acidic overall water splitting application. α-Ni(OH)2@Ir requires lower overpotentials (238 mV and 20 mV) to achieve 10 mA cm−2 in acidic OER and HER catalysis compared to benchmarked IrO2 (332 mV) and Pt/C (36 mV); meanwhile, the OER mass activity at 1.55 V vs. RHE was 92 fold higher than IrO2; HER mass activity at overpotential of 80 mV was 5 fold better than Pt/C. The boosted catalytic activity is due to the enhanced utilization efficiency of Ir stemmed from the ultrathin Ir shell (~1 nm). Moreover, 1.49 V is demanded for α-Ni(OH)2@Ir to attain 10 mA cm−2 in acidic overall water splitting, 110 mV lower than benchmarked Pt/C-IrO2 system. Meanwhile, stable catalytic performance is recorded for 20 h.

Electrodeposition-fabricated catalysts for polymer electrolyte water electrolysis

Water electrolysis using renewable energy sources such as solar and wind power has the advantage of producing hydrogen with high efficiency and zero emissions. Solid polymer electrolyte water electrolysis (SPEWE) is divided into anion exchange membrane electrolysis (AEMWE) carried out in an alkaline environment and proton exchange membrane electrolysis (PEMWE) carried out in an acidic environment. Research on the electrocatalysts used in these electrolysis procedures has focused on the development of transition metal-based catalysts with catalytic activity, high stability, and low cost that can replace the currently used noble-metal based electrocatalysts. Among the various electrocatalyst fabrication methods, electrodeposition can be used to fabricate catalysts in a simple manner at low cost and high purity. In addition, catalysts can be directly electrodeposited onto a substrate such as a gas diffusion layer, simplifying the electrode fabrication process and readily enabling the advantageous control of the physical, chemical, structural, and compositional properties of the catalyst. In this paper, we summarize the characteristics and structures of the water electrolysis catalysts prepared by the electrodeposition method based on recent research studies that suggest their applicability to practical water electrolysis systems in the future.

Electrochemical fabrication of IrOx nanoarrays with tunable length and morphology for solid polymer electrolyte water electrolysis

For a typical Proton exchange membrane (PEM) water electrolysis system, reducing the amount of Ir loading at the anode in membrane electrode assembly (MEA), while maintaining the performance, is still a big challenge. Here, to improve the performance of catalyst layer for oxygen evolution reaction (OER) in an acidic medium, vertical aligned IrOx nanoarrays (IrOx NAs) were synthesized by electrodeposition with TiO2 nanotube arrays (TNTA) as template. By tuning the scan rate in the electrodeposition process, IrOx open-end nanotube arrays with tunable length ranged from 500 nm to 1400 nm and hollow nanorod arrays were obtained due to a diffusion-controlled deposition process. By constructing 3-D electrode of 1-D catalyst with enhanced ion transfer, IrOx NAs performed almost the same current density of OER with 1/20 Ir loading amount compared with commercial IrO2 nanoparticles, which could significantly reduce the cost of catalyst in PEM water electrolyser. Moreover, no apparent current decrease was observed even after 10 h’ anodic polarization under 1.55 V, which exhibit excellent OER durability.

Operando Sub-Second Neutron Imaging of Cationic Species Migration in a Proton Exchange Membrane Water Electrolyzer

In recent years, it became clear that implementing energy storage on a large scale is a necessary route for the power production sector to maintain a stable and sustainable grid with increasing share of intermittent renewable sources of energy. Proton exchange membrane water electrolyzers show promise especially because of their suitability to be coupled to renewables in remote areas decentralizing the energy grid. There are, however, some challenges, which have to be tackled before market penetration can occur. One of the most pressing issues is the susceptibility of the proton exchange membrane to feed water impurities in form of cations [1], [2]. Titanium porous transport layers, piping and other system components will introduce slight amounts of cations during normal operation (Fe, Na, Cu, Ca, Ti), which over a longer period will become the cause of significant overpotential [3]. It is therefore necessary to understand the contamination mechanism of proton exchange membranes and its impact on the electrochemical performance of the cell. Motivated by the fact that the reversible degradation is one of the key factors which dictate the operability of an electrolyzer, we carried out experiments which bring further insights into the influence and behavior of the cationic species in the proton exchange membrane water electrolyzer under operation and standby conditions. Neutron imaging techniques were employed to observe the model contaminant in form of Gd3+, which is a perfect fit due to its large neutron cross-section. We found that under the effect of the electric field the cations migrate and accumulate near cathode catalyst layer/porous transport layer interface. A sub-second imaging setup enabled us to correlate the position of cations within the membrane with electrochemical data. Subsequently we regenerated the cell by operating it with diluted sulfuric acid (below 1mMol/L) injected into cathode compartment during the neutron imaging. Influence of the accumulation of the cations near the cathode catalyst layer on the electrolyzer performance and optimal operando regeneration procedures will be discussed. [1] S. Sun, Z. Shao, H. Yu, G. Li, and B. Yi, “Investigations on degradation of the long-term proton exchange membrane water electrolysis stack,” J. Power Sources, vol. 267, pp. 515–520, 2014. [2] X. Wang, L. Zhang, G. Li, G. Zhang, Z. G. Shao, and B. Yi, “The influence of Ferric ion contamination on the solid polymer electrolyte water electrolysis performance,” Electrochim. Acta, vol. 158, pp. 253–257, 2015. [3] U. Babic, M. Suermann, F. N. Büchi, L. Gubler, and T. J. Schmidt, “Critical Review—Identifying Critical Gaps for Polymer Electrolyte Water Electrolysis Development,” J. Electrochem. Soc., vol. 164, no. 4, pp. F387–F399, 2017. Figure 1

Preparation of Sb-Doped SnO2 Nanoparticle with High Surface Area for Use As a Stable Anode Catalyst Support for PEM Electrolyzers.

Proton exchange membrane (PEM) water electrolysis has been considered as one of the most promising technologies for large H2 production. While the cost and stability of PEM are the main obstacles for the commercial application. Here we report a cost-effective catalyst, which consists of IrO2 nanoparticles supported on Sb-doped SnO2 (ATO). ATO support is synthesized by using templating process and hydrothermal method to improve its thermal stability. It has a mesoporous structure, small particle size, and high surface area. After loading IrO2 via Adams fusion method, the IrO2/ATO catalyst shows high electrochemical stability, according to repetitive potential cycling. This catalyst also shows a good electrochemical performance in single cell. Firstly, we prepared a series of ATO samples and named them as the Brunauer Emmett Teller model (BET) surface area. The surface area and pore size distribution of the obtained ATO samples were calculated by BET and nonlocal density functional theory (NLDFT). As shown in Fig.1a, the pore size become smaller with the increases of BET surface area, and the high surface area may be contributed to high synthesize temperature and long synthesize time. Secondly, we use the as-prepared ATO samples as catalysts support for IrO2, the catalysts named as BET surface area-IrO2 (e.g. 107-IrO2) and the IrO2 loading is 40 wt%. Fig.1b shows the cyclic voltammetry (CV) performance of different catalysts, it is quite clear that when supported by ATO, the voltammograms of these supported catalysts are dissimilar in shape from that of unsupported IrO2. The electrochemically active surface area (ECSA) of 170-IrO2 is obvious higher than the other ATO supported catalyst and a little higher than pure IrO2. This indicate that the 170 sample has the appropriate surface area as well as pore size distribution and it is best used as for IrO2 catalyst support. Finally, the accelerated degradation testing (ADT) was performed to investigated the durability of the 170-IrO2 catalyst in rotating disk electrode (RDE) test. As shown in Fig.1c the CV curves almost overlap before and after 9000 cycles’ ADT. Fig.1d shows the Linear sweep voltammetry (LSV) results of the catalyst samples before and after ADT. It is quite obvious that the 170-IrO2 catalyst is maintained stable with only a little loss in the catalytic activity. We have successfully made a series of ATO through templating process followed by hydrothermal method with different BET surface area and used as catalyst support for IrO2. The 170-IrO2 catalyst demonstrates high electrochemical performance and good stability. Herein, the as-synthesized ATO is considered to be a promising oxygen evolution catalyst support for solid polymer electrolyte water electrolyzer applications. Figure 1

Iridium-Based Catalysts for Solid Polymer Electrolyte Electrocatalytic Water Splitting.

Chemical energy conversion/storage through water splitting for hydrogen production has been recognized as the ideal solution to the transient nature of renewable energy sources. Solid polymer electrolyte (SPE) water electrolysis is one of the most practical ways to produce pure H2 . Electrocatalysts are key materials in the SPE water electrolysis. At the anode side, electrode materials catalyzing the oxygen evolution reaction (OER) require specific properties. Among the reported materials, only iridium presents high activity and is more stable. In this Minireview, an application overview of single iridium metal and its oxide catalysts-binary, ternary, and multicomponent catalysts of iridium oxides and supported composite catalysts-for the OER in SPE water electrolysis is presented. Two main strategies to improve the activity of an electrocatalyst system, namely, increasing the number of active sites and the intrinsic activity of each active site, are reviewed with detailed examples. The challenges and perspectives in this field are also discussed.

Communication—Deuterium Isotope Separation by Solid Polymer Electrolyte Water Electrolysis

Electrolytic deuterium (D) separation from protium-containing solution has been investigated. Proton (PEM) and anion exchange membrane (AEM) electrolysis were performed at constant current. The mass analysis of hydrogen gas and water vapor was carried out. For both PEM and AEM electrolysis, the D concentration in the evolved hydrogen gas was lower than that of the initial electrolytic solution. The D concentration in the water vapor was unchanged by PEM electrolysis, but was increased by AEM. The separation factor of PEM was smaller than that of AEM, which was attributed to the humidification state on platinum catalyst.

Synthesis and activities of IrO2/Ti1−xWxO2 electrocatalyst for oxygen evolution in solid polymer electrolyte water electrolyzer

Novel IrO2/Ti1−xWxO2 electrocatalysts for the oxygen evolution reaction (OER) in a solid polymer electrolyte (SPE) water electrolyzer were synthesized using the Adams fusion method and the evaporation-induced self-assembly method. Physical and chemical characterizations of the sample—including Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and polarization curves for single cells—were performed. The W-doped TiO2 support with various doping amounts (0, 5, 10, and 20at.%) exhibited a single-phase anatase structure and a large BET surface area. Furthermore, with annealing at a reducing atmosphere, a phase change from anatase to rutile occurred, trace α-W was precipitated from the crystal lattice of the Ti0.8W0.2O2 sample, and the BET surface area decreased accordingly. On the other hand, the conductivities of the W-doped support exhibited an increasing trend, indicating a significant impact of the W dopant on the enhancement of the TiO2 conductivity. The voltammetric charge of 40IrO2/Ti0.9W0.1O2 (1754mC (cm2mg)−1) was higher than that of unsupported IrO2, and 40IrO2/Ti0.9W0.1O2 exhibited enhanced electrochemical activity for the OER process. A single-cell performance of 1.79V was achieved by using 80IrO2/Ti0.9W0.1O2 as an anode for the minimum charge-transfer resistance and ohmic resistance. Electrocatalysts with the Ti0.9W0.1O2 support exhibited good durability. Thus, Ti0.9W0.1O2 is a promising anode electrocatalyst support for SPE water electrolysis.

Computational fluid dynamics study on the anode feed solid polymer electrolyte water electrolysis

A steady-state two-dimensional model for the anode feed solid polymer electrolyte water electrolysis (SPEWE) is proposed in this paper. Finite element procedure was employed to calculate the multicomponent transfer model coupled with fluid flow in flow channels and gas diffusion layers and electrochemical kinetics in catalyst reactive surface. The performance of the anode feed SPEWE predicted by this model was compared with the published experimental results and reasonable agreement was reached. The results show that oxygen mass fraction increases because of the water oxidation when water flows from the import to the export on the anode side. On the cathode side, hydrogen mass fraction varies little since hydrogen and water mix well. The flux of water across the electrolyte increased almost linearly with the increase of the applied current density. Since the ohmic overpotential loss increasing as the solid polymer electrolytes’ thickness increasing, the performance of the anode feed SPEWE with Nafion 112, 115, 117 decreases at the same applied current density.

Investigation of V-doped TiO2 as an anodic catalyst support for SPE water electrolysis

A modified evaporation-induced self-assembly (EISA) method was employed to prepare titania samples doped with different amounts of vanadium (0, 10, 20, 30 at.%), which were further evaluated as catalyst supports for the oxygen evolution reaction (OER) catalyst IrO2 in the solid polymer electrolyte water electrolyzer (SPEWE). The effects of V dopant on titania supports are proved to be twofold: i) enhancing the simplification of phase composition and consequently improving the homogeneity of porous morphology; ii) introducing redox couple V (IV)/V (V) to the surface of titania. As a result, the catalyst's OER activity is improved with the increase of V dopant in the titania support after loading IrO2 via Adams fusion method. In single cells, the OER performance gradually increases with V dopant from 0 to 20 at.%, followed by a performance deterioration with V amount reaching 30 at.% due to the corrodible V2O5 precipitate.

Investigation of Mesoporous Niobium-Doped TiO2as an Oxygen Evolution Catalyst Support in an SPE Water Electrolyzer

Titania doped by niobium was successfully synthesized via a modified evaporation-induced self-assembly method (EISA) as a support of IrO2 for a solid polymer electrolyte water electrolyzer (SPEWE). The doping amount of niobium (5, 10, 20 at. %) was emphatically investigated to evaluate the effects on nanostructure, morphology, and oxygen evolution reaction (OER) activity of Nb-doped titania supported IrO2. The high-resolution transmission electron microscopy (TEM) results show that IrO2 supported by Nb-doped titania exhibits grain refinement and uniform dispersion. An investigation of the electrocatalytic activity by half-cell electrochemical testing reveals that the Nb-doped titania supported IrO2 catalyst demonstrates significant OER activity. When the Nb content reaches 20 at. % in the support, the Nb-doped titania supported IrO2 possesses the highest OER activity, which is superior to that of pristine titania supported IrO2 and unsupported IrO2. The single-cell tests also prove that 20 at. % is the be...

A Npg-Based Ultra-Thin Anode Catalyst Layer for Spewe

Nanoporous gold (NPG) has a long history of application. By electrochemical or chemical removal of Ag from AgAu alloy, the remaining gold undergoes a self-organization process forming a 3D bicontinuous network with interconnected ligaments. Due to its relatively high surface area, high conductivity, small size ligament and 3D bicontinuous porous structure, NPG has found its way in electrocatalysis, bio-sensors, and fuel cells. By extending dealloy time or thermal coarsening temperature; the structure of NPG can be easily tuned. In this paper, a facile method was proposed for a novel MEA applied in solid polymer electrolyte water electrolysis (SPEWE). NPG with a thickness of 100 nm dealloyed from 12K gold foil was employed as substrate. IrO2 was deposited onto its surface via a conventional thermal decomposition method. A loading of IrO2 as low as 50 μg cm-2 was achieved in this experiment while keeping an acceptable performance. With a IrO2 loading of 0.2 mg cm-2，the performance was 1.686 V@ 1000 mA cm-2 at 80 ºC. Scanning electron microscopy measurement showed that IrO2 formed a uniform thin layer on the surface of NPG. The maximum thickness is 500 nm, which is only 1/20 to the conventional catalyst layer. The ultra-thin catalyst layer eased the transport of reactant and product, which reasonably explicated the remarkable performance. During the stability test, the cell voltage was constant over 200 h at 250 mA cm-2. The result here demonstrated that an ultra-thin catalyst layer with a low IrO2 loading could applied in real solid polymer electrolyte water electrolyzer.

The influence of Ferric ion contamination on the solid polymer electrolyte water electrolysis performance

Fe3+ is a sort of common metal ion contaminant for the solid polymer electrolyte (SPE) water electrolyser. In this paper, the effect of Fe3+ on the performance of SPE water electrolyser has been investigated by both in-situ and ex-situ characterizations. The electron probe microanalysis and ultraviolet test results showed that Fe3+ could migrate from the anode to the cathode and mostly be reduced to Fe2+ in the cathode rather than occurred underpotential deposition as described in the previous report. The in-situ dynamic contamination test showed that the anode voltage increased sharply as soon as the Fe3+ was fed into the anode, while the cathode voltage kept constant until the contamination time was over 30minutes, indicating the higher tolerance of the cathode than the anode for the Fe3+ contamination. The calculation results based on the electrochemistry impedance spectroscopy test results revealed that the striking increase of the electrolysis voltage was mainly attributed to the ohmic overpotential, which was due to the replacement of H+ by Fe3+ in the Nafion resin. Interestingly, the voltage lagged behind the current for several minutes in the multi-current-step test for the contaminated electrolyser, which phenomenon may be used for judging whether the SPE water electrolyser performance degradation is due to the metal ions contamination. Furthermore, recovery strategy has been developed, and it was found that the contaminated electrolyser could be mostly recovered by 0.5M H2SO4 solution treatment for 13h.

Solvent Induced Fabrication of Solid Polymer Electrolyte Water Electrolyzer: A study in Sulfonated Poly(Ether Ether Ketone) Based Membrane Electrode Assembly

AbstractA novel solvent induced fabrication technique is developed for the preparation of the sulfonated poly (ether ether ketone) (sPEEK) based water electrolysis membrane electrode assembly (MEA). The solvent, dimethyl formamide (DMF), instead of the high pressure and temperature, is used to induce the softening of the membrane and better integration of the MEA with excellent interface compatibility. The influence of hot pressing period, the amount of polymer used in the electrode, and the temperature are investigated to optimize the performance of the MEA. The single cell performance for the water electrolysis is evaluated to optimize the fabrication parameters. It is found out that all three factors have great influences on the final cell performance and the tradeoff effects are observed due to the various states of the catalyst efficiency, TPBs, the conductivity, and cell resistance. As a result, the cell performance is optimized with the MEA fabricated at 120 °C, using the catalysts to polymer weight ratio of 5:1 and a 60s hot pressing period.

Proton exchange membrane water electrolysis with short-side-chain Aquivion® membrane and IrO2 anode catalyst

A series of three membrane types has been screened for medium temperature solid polymer electrolyte water electrolysis in membrane electrode assemblies coated with 2 mg cm−2 of iridium oxide as a catalyst for the oxygen evolution reaction, synthesised via a hydrolysis method from the hexachloroiridic acid precursor, and deposited on the membrane either directly by spray deposition or by decal transfer. The short-side-chain perfluorosulfonic acid Aquivion® ionomer of equivalent weight 870 meq g−1, in membranes of thickness 120 μm, gives higher water electrolysis performance at 120 °C than a composite membrane of Aquivion® with zirconium phosphate, while a sulfonated ether-linked polybenzimidazole, sulfonated poly-[(1-(4,4′-diphenylether)-5-oxybenzimidazole)-benzimidazole], shows promising performance and no transport limitations up to 2 A cm−2. The lowest cell voltage was observed at 120 °C for an MEA prepared using spray-coating directly on the Aquivion® membrane, 1.57 V at 1 A cm−2.

Membrane electrode assemblies with low noble metal loadings for hydrogen production from solid polymer electrolyte water electrolysis

High performance membrane electrode assemblies (MEAs) with low noble metal loadings (NMLs) were developed for solid polymer electrolyte (SPE) water electrolysis. The electrochemical and physical characterization of the MEAs was performed by I–V curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Even though the total NML was lowered to 0.38 mg cm−2, it still reached a high performance of 1.633 V at 2 A cm−2 and 80 °C, with IrO2 as anode catalyst. The influences of the ionomer content in the anode catalyst layer (CL) and the cell temperature were investigated with the purpose of optimizing the performance. SEM and EIS measurements revealed that the MEA with low NML has very thin porous cathode and anode CLs that get intimate contact with the electrolyte membrane, which makes a reduced mass transport limitation and lower ohmic resistance of the MEA. A short-term water electrolysis operation at 1 A cm−2 showed that the MEA has good stability: the cell voltage maintained at ∼1.60 V without distinct degradation after 122 h operation at 80 °C and atmospheric pressure.

Preparation and characterization of partial-cocrystallized catalyst-coated membrane for solid polymer electrolyte water electrolysis

A novel catalyst-coated membrane (CCM) for solid polymer electrolyte water electrolysis was fabricated by together crystallizing partial-crystallized Nafion membrane and catalyst layers. The properties and performance of the partial-cocrystallized CCM (PCCCM) were evaluated and analyzed by destructive soaking test, scanning electron microscope, mercury intrusion and single cell test. The results revealed that the optimum annealing temperature and time for fabricating partial-crystallized Nafion membrane and PCCCM was 100 °C for 4 h and 120 °C for 4 h, respectively. The PCCCM not only possessed much stronger cohesion between membrane and catalyst layers, but also had higher porosity than conventional CCM. The electrolysis voltage of the SPE water electrolyser with the new CCM was as low as 1.748 V at 2000 mA cm−2 under 80 °C and atmospheric pressure. Moreover, there was no obvious increase of electrolysis voltage during stability test conducted under 2000 mA cm−2 for about 180 h.

A cocrystallized catalyst-coated membrane with high performance for solid polymer electrolyte water electrolysis

A cocrystallized catalyst-coated membrane (CCM) is prepared by together heating amorphous Nafion membrane and catalyst layers at 120 °C to develop the membrane electrode assembly for solid polymer electrolyte (SPE) water electrolysis. The cocrystallization treatment effectively reinforces the bonding between membrane and catalyst layers, and increases the hydrophobicity of the catalyst layers. The SPE water electrolyser with the cocrystallized CCM decreased cell voltage by 0.09 V at 2000 mA cm−2 at 80 °C and improved the stability in comparison with the conventional CCM.

The dynamic-state effects of sodium ion contamination on the solid polymer electrolyte water electrolysis

Na+ is a likely intrinsic impurity in water and is a potential cation impurity in the solid polymer electrolyte water electrolysis. In this paper, the dynamic-state effect of low concentration of Na+ is studied by adding Na+ into the deionized water fed in the SPE water electrolyser. The dynamic variation of cell voltage results show that the cell performance degraded more severely in the presence of Na+ impurity by anode poisoning than by cathode poisoning. The severity and poisoning rate of the cell depend on the Na+ concentration, water flow rate and cell temperature. However, the current density does not impact the extent of the cell voltage increase. In the meantime, an external reference electrode is used to measure the anode and cathode potentials. The performance degradation is mainly ascribed to the increase in cathode overpotential by anode poisoning. EIS measurements show that the performance difference primarily comes from the kinetics loss rather than the ohmic loss. The decrease of available protons in the three phase boundaries may lead to the increase in charge transfer resistance. The electron probe microanalysis tests show that Na+ remains in CCM even recovered with deionized water, which results in only partially recovered cell performance.

Highly effective IrxSn1−xO2 electrocatalysts for oxygen evolution reaction in the solid polymer electrolyte water electrolyser

We developed an advanced surfactant-assistant method for the Ir(x)Sn(1-x)O(2) (0 < x ≤ 1) nanoparticle (NP) preparation, and examined the OER performances by a series of half-cell and full-cell tests. In contrast to the commercial Ir black, the collective data confirmed the outstanding activity and stability of the fabricated Ir(x)Sn(1-x)O(2) (x = 1, 0.67 and 0.52) NPs, which could be ascribed to the amorphous structure, good dispersion, high pore volume, solid-solution state and Ir-rich surface for bi-metal oxides, and relatively large size (10-11 nm), while Ir(0.31)Sn(0.69) exhibited poor electro-catalytic activity because of the separated two phases, a SnO(2)-rich phase and an IrO(2)-rich phase. Furthermore, compared with highly active IrO(2), the improved durability, precious-metal Ir utilization efficiency and correspondingly reduced Ir loading were realized by the addition of Sn component. When the Ir(0.52)Sn(0.48)O(2) cell operated at 80 °C using Nafion® 115 membrane and less than 0.8 mg cm(-2) of the noble-metal Ir loading, the cell voltages we achieved were 1.631 V at 1000 mA cm(-2), and 1.821 V at 2000 mA cm(-2). The IR-free voltage at the studied current density was very close to the onset voltage of oxygen evolution. The only 50 μV h(-1) of voltage increased for the 500 h durability test at 500 mA cm(-2). In fact, these results are exceptional compared to the performances for OER in SPEWE cells known so far. This work highlights the potential of using highly active and stable IrO(2)-SnO(2) amorphous NPs to enhance the electrolysis efficiency, reduce the noble-metal Ir loading and thus the cost of hydrogen production from the solid polymer electrolyte water electrolysis.