Chapter Four · failure evidence
What Metal Oxide Material Engineering got wrong, from 53 dissertations
The evaluated records describe various failure mechanisms encountered when synthesizing, doping, and integrating metal oxide materials across catalytic, electrochemical, and optoelectronic applications. These engineering failures predominantly arise from dopant solubility limits, operational phase transformations, excessive material loading, interfacial transport defects, and detrimental reductive treatments. These records come from PhD theses at 17 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Dopant and cation substitution causes structural degradation, volatilization, or inactive cluster formation
High-concentration cation substitution, surface doping, or anion doping often exceeded solubility limits and caused severe structural degradation or secondary phase segregation. Furthermore, altering dopant concentrations frequently resulted in dopant volatilization at elevated temperatures, loss of isolated catalytic sites into inactive clusters, or rapid capacity fading during cycling.
Tried and failed
transition metal oxide high-concentration surface doping applied to semiconductor photoanodes for pollutant degradation. Outcome: worse than baseline. Reason: excessive loading lowered the valence band redox potential too much, reducing oxidation capacity
The Development of Energy Efficient Wastewater Treatment: Electrochemical Oxidation and PFACs liquid-liquid Extraction · Georgia Tech
Tried and failed
transition metal surface termination doping applied to perovskite oxide oxygen reduction catalysts. Outcome: worse than baseline. Reason: terminating with B-site cations or inert metals decreased catalytic activity and increased polarization resistance
Tried and failed
High-temperature chemical anion doping applied to oxide nanoparticle electrocatalysts. Outcome: worse than baseline. Reason: Severe structural degradation of nanoparticles led to reduced oxygen evolution reaction activity
Polymer-Ligated Nanocrystals with Tunable Dimensions, Compositions, and Architectures · Georgia Tech
Tried and failed
transition metal oxide doping via air sintering applied to zirconia-based ceramic solid solutions. Outcome: unstable. Reason: Severe dopant volatilization above 1273 K with low solubility and preferential partitioning into secondary phases
Towards Crack-Resistant Polycrystalline Zirconia Shape-Memory Ceramics with Low Hysteresis · MIT
Tried and failed
high-concentration metal cation substitution applied to perovskite oxide catalysts. Reason: exceeded the dopant solubility limit and could not maintain required transition metal oxidation states
Activity and Stability Design Principles of Transition Metal Compounds for Decarbonization · MIT
Tried and failed
omitting dopants in high-entropy transition metal oxides applied to battery anode materials. Outcome: unstable. Reason: loss of specific dopant cations caused rapid capacity degradation during high-rate extended cycling
Development of niobium-based oxide anodes with the Wadsley-Roth shear structure for fast-charging and durable lithium-ion batteries · Georgia Tech
Tried and failed
aliovalent cation solid solution doping applied to oxide thin-film battery electrodes. Outcome: unstable. Reason: severe capacity fading and poor cycling stability despite high initial discharge capacity
Tried and failed
indium promoter addition to supported copper catalysts applied to heterogeneous carbon dioxide hydrogenation. Outcome: worse than baseline. Reason: Decreased active metal dispersion and reduced concentration of reducible oxide support oxygen vacancies
Tried and failed
increasing metal dopant loading in zeolite catalysts applied to methane catalytic oxidation. Outcome: worse than baseline. Reason: excessive metal loading formed inactive oxide clusters instead of active isolated sites, lowering turnover frequency
Design and Engineering of Carbon Fixing Material Systems · MIT
Operational stress causes phase degradation, mechanical damage, and loss of functional properties
Extended cycling, thermal treatments, and continuous operational conditions frequently triggered microcracking, material dissolution, and irreversible phase transformations into inactive binary oxides. Similarly, reducing nanoparticle size or altering defect states created excessive grain boundary trapping, optical degradation, and early sensor or catalytic deactivation.
Tried and failed
high-temperature calcination of catalyst precursor applied to supported metal oxide photocatalyst composite. Outcome: worse than baseline. Reason: phase transformation into oxide decreased photocatalytic degradation efficiency and degraded catalytic reusability over cycles
Porous Heterogeneous Hierarchical Materials for Environmental Applications · Cornell
Tried and failed
tethering molecular photooxidants to metal oxide catalysts applied to photoelectrochemical water oxidation. Outcome: unstable. Reason: dye molecules detached under operating conditions and underwent oxidative degradation rather than driving catalysis
Tried and failed
photocatalytic water splitting using mixed-metal oxide applied to strontium copper oxide photocatalysts. Outcome: unstable. Reason: the material degraded into binary copper oxides under operational photocatalytic conditions
Tried and failed
low-cost metal-oxide semiconductor gas sensors applied to continuous methane monitoring in anaerobic digestion. Outcome: unstable. Reason: sensor reliability issues prevented consistent methane concentration measurement over continuous multi-day operation
Enhancement of Biogas Production During Start-Up Operations of the Anaerobic Digestion of Wastewater Sludge · Queens University Institutional Repository
Tried and failed
nanoparticle size reduction for chemiresistive sensing applied to metal oxide gas sensors. Outcome: worse than baseline. Reason: excess grain boundaries caused electron trapping and recombination, reducing overall sensor response despite higher surface area
Low-cost and Low-emissions Strategies for Implementation of Hydrogen as Next Generation Fuel · MIT
Tried and failed
large range potential cycling applied to perovskite thin-film oxide electrodes. Outcome: unstable. Reason: induced microcracking or delamination, causing irreversible impedance changes
Tried and failed
iodide substitution in perovskite photocatalyst composites applied to photocatalytic carbon dioxide reduction. Outcome: unstable. Reason: rapid photo-induced phase segregation and material degradation under illumination
Development of semiconductors for the photocatalytic production of solar fuels · Imperial
Tried and failed
Noble metal nanoparticle decoration on defective metal oxides applied to electrocatalytic oxygen evolution reaction. Outcome: worse than baseline. Reason: High surface oxygen vacancy coverage suppresses electrocatalytic activity upon gold nanoparticle introduction
Tried and failed
extended pyrolysis duration for carbon-metal oxide composites applied to battery cathode materials. Outcome: worse than baseline. Reason: prolonged thermal treatment degraded structural stability leading to rapid capacity fading after initial cycling
Excessive active material loading and deposition thickness cause pore blockage, high resistance, and optical scattering
Increasing metal oxide mass loading, cyclic electrodeposition, or hydrate concentration caused nanoparticle aggregation, pore blockage, and elevated electrical resistance. In optical and photothermal applications, these high loadings resulted in parasitic light scattering and substantial optical losses that undermined performance.
Tried and failed
adding metal oxide co-catalysts applied to photothermal polymer depolymerization. Outcome: worse than baseline. Reason: scattered light and reduced photothermal absorber light absorption, lowering yields
Considered and rejected
Considered and rejected: Rejected conducting photothermal depolymerization in the presence of basic metal oxides (ZnO, BaO, CaO, MgO), as they scattered light and decreased styrene yield compared to carbon black alone.
Considered and rejected
Considered and rejected: Rejected high titanium oxide hydrate content (>80 vol%) hybrid formulations due to poor thin-film processability and premature TiO2 nanoparticle formation/aggregation leading to optical loss.
Elucidating exciton-polaritons in organic and two-dimensional metal halide semiconductors · Georgia Tech
Tried and failed
high mass loading of electrodeposited metal oxide applied to porous carbon supercapacitor electrodes. Outcome: unstable. Reason: active material dissolution and structural degradation during cycling
Electrochemical studies of the applications of novel carbon-based materials · Oxford
Tried and failed
prolonged electrodeposition of metal oxide applied to porous carbon supercapacitor electrodes. Outcome: worse than baseline. Reason: excessive active material loading increased electrical resistance, reducing specific capacitance at high scan rates
Electrochemical studies of the applications of novel carbon-based materials · Oxford
Tried and failed
high metal-oxide nanoparticle loading in carbon nanocomposite inks applied to printed microsupercapacitor electrodes. Outcome: worse than baseline. Reason: nanoparticle clustering severely degraded electrochemical capacitance compared to additive-free electrodes
Tried and failed
excessive cyclic electrodeposition of metal oxide coatings applied to pseudocapacitive carbon nanotube electrodes. Outcome: worse than baseline. Reason: increasing deposition cycles degraded capacitive performance, likely due to pore blockage or excessive film resistance
Tried and failed
excessive metal oxide deposition on porous sorbents applied to adsorptive water contaminant removal. Outcome: worse than baseline. Reason: overloading blocked adsorbent pores and reduced accessible active surface area, decreasing overall adsorption capacity
Treatment of Aqueous Arsenic Using Chemically and Electrochemically Modified Biomaterials · HARVEST
Interfacial defects, pinholes, and band misalignment degrade charge transport layer efficiency
Metal oxide transport layers frequently introduced high contact resistance, interfacial oxidation, pinholes, and unfavorable band alignments that caused severe voltage hysteresis or electrical shorting. In addition, defective oxide interfaces and carrier mobility degradation undermined overall device fill factors and power conversion efficiencies.
Tried and failed
chemical vapour deposition of transition metal catalysts applied to photoelectrode surface functionalisation. Outcome: worse than baseline. Reason: produced mixed amorphous oxide/hydroxide phases instead of the active pure oxyhydroxide phase obtained via solution methods
Tried and failed
conducting polymer photosensitization of metal oxide photocatalysts applied to visible light photocatalytic degradation. Outcome: no signal. Reason: incompatible HOMO-LUMO energy band alignment with the titanium dioxide conduction band
Electrospun Electroactive Polymer Nanocomposites for Water Purification · TXST Digital Repository
Tried and failed
single-layer titanium dioxide electron transport layer applied to planar perovskite solar cells. Outcome: unstable. Reason: severe light- and UV-induced degradation caused by titanium dioxide photocatalytic and interfacial instability
Composition and Interface Engineering of High Performing Perovskite Solar Cells · EPFL
Tried and failed
peroxide surface treatment for defect passivation applied to metal oxide electron transport layers. Outcome: worse than baseline. Reason: failed to eliminate hysteresis as effectively as alternative surfactant or halide dopants
Tried and failed
mesoporous metal oxide hole transport layer integration applied to tin-based perovskite solar cells. Reason: devices suffered complete electrical shorting due to pinholes and reduced film grain size
Fabrication and characterization of lead-free and lead based perovskite solar cells · Imperial
Tried and failed
nickel oxide hole transport layer substitution applied to tin-based perovskite solar cells. Outcome: worse than baseline. Reason: poor interfacial contact and interfacial oxidation causing severe S-shaped J-V curves
Fabrication and characterization of lead-free and lead based perovskite solar cells · Imperial
Lost to a baseline
Bare MTO without PEDOT:PSS in p-i-n perovskite solar cells achieved only 0.5% PCE and 30% FF compared to 6.4% PCE with PEDOT:PSS due to oxide interface defects/insulating nature.
Oxide layer design for transparent electrodes and charge transport components Oxidschichtdesign für transparente Elektroden und Ladungstransportkomponenten · DSpace-CRIS at TU Wien
Considered and rejected
Considered and rejected: Rejected transition metal oxides (MoO3, V2O5) surface-transfer doping due to drastic carrier mobility degradation at high carrier densities and integration difficulty
Diamond on GaN integration for power semiconductor devices with efficient thermal management · EPFL
Inappropriate reduction conditions cause unwanted phase transformations and catalytic deactivation
Applying cathodic potentials or reductive regeneration protocols often converted active oxides into inactive hydroxides or failed to clear carbonaceous deposits. Similarly, exposure to reducing environments at inappropriate temperatures either promoted reverse reactions, lowered catalytic activity, or caused metallic reduction and coking.
Tried and failed
transition metal doping in perovskite catalyst applied to solid oxide fuel cell anodes. Outcome: unstable. Reason: Dopants reduced to metallic phase under hydrocarbons, causing rapid coking and cell degradation
Development of Novel Electrode and Catalyst Materials for Solid Oxide Electrochemical Cells · Georgia Tech
Tried and failed
potentiostatic anodic electrodeposition of transition metal oxides applied to boron-doped diamond electrodes. Reason: electrodeposition produced inactive lower-valent oxides (Mn2O3/Mn3O4) instead of pseudocapacitive MnO2, yielding negligible capacitive currents
Electrochemical studies of the applications of novel carbon-based materials · Oxford
Tried and failed
cathodic reductive potential regeneration applied to deactivated metal oxide electrocatalysts. Outcome: worse than baseline. Reason: negative potential caused irreversible phase transformation from active oxide to inactive hydroxide
Tried and failed
reductive catalyst regeneration applied to deactivated supported metal oxide catalysts. Reason: reduction cycles alone cannot remove carbonaceous deposits without oxidative treatment
Surface Reactions of Biomass Derived Oxygenates on Lewis Acidic Metal Oxides · Georgia Tech
Tried and failed
low-temperature hydrogen reduction of base metal oxides applied to supported iron-based heterogeneous catalysts. Reason: reduction temperature was insufficient to reduce magnetite to metallic iron phase
Dilute Alloy Catalysts for the Synthesis of Isobutanol via the Guerbet Route: A Comprehensive Study · EPFL
Tried and failed
pre-reduction of supported metal oxide catalyst applied to water-gas-shift catalytic activity. Outcome: worse than baseline. Reason: reduction lowered catalytic activity compared to the unreduced state
Tried and failed
re-reduction after ambient air exposure applied to supported copper catalysts. Outcome: worse than baseline. Reason: promoted reverse water-gas shift reaction yielding carbon monoxide over methanol
Competitive adsorption, surface site blocking, and parasitic phase formation impede functional activity
Active sites on metal oxide surfaces were frequently obstructed by background salts, electrostatically bound cations, or direct polymer grafting that heightened charge transfer resistance. In other systems, secondary substrate oxygen sources or inactive secondary oxide phases added dead mass and encouraged undesired phase formation.
Tried and failed
photocatalytic pollutant oxidation using mixed-metal oxide catalysts applied to high-salinity wastewater treatment. Outcome: too slow. Reason: competitive adsorption of background salts onto catalyst active sites inhibited reactant binding
Considered and rejected
Considered and rejected: Rejected using oxide substrates (e.g. SiO2) for Ti-containing TMD sulfurization because substrates act as secondary oxygen sources promoting TiOx formation
Developing transition metal dichalcogenide alloys for applications to integrated photonics · MIT
Tried and failed
direct covalent polymer grafting via esterification applied to metal oxide nanoparticle electrode slurries. Outcome: worse than baseline. Reason: caused severe capacity fade, poor rate capability, and high charge transfer resistance
Understanding interfacial phenomena for the creation of next-generation high-capacity battery electrodes · Georgia Tech
Considered and rejected
Considered and rejected: Rejected introducing secondary conductive oxide phases (such as CuGeO3) into GeO2 composites because they add electrochemically inactive dead mass and reduce theoretical capacity.
High Loading Oxide Anodes For Lithium Ion Batteries Via A Superelastic Graphene Composite Approach · Penn
Considered and rejected
Considered and rejected: Rejected non-acidified regeneration cycles for iron oxyhydroxide because electrostatically bound Na+ and Ca2+ blocked active sites and caused rapid loss of adsorption capacity.
Tried and failed
hydrothermal aging of transition metal zeolite catalysts applied to selective catalytic reduction of nitrogen oxides. Reason: active metal species irreversibly agglomerate into inactive oxide clusters, causing nonselective oxidation
The simultaneous Selective Catalytic Reduction of N2O and NO over Fe-exchanged zeolites · EPFL
Left open by the authors
Problems the authors named and did not get to.
Left open
Synthesize and integrate bimetallic or oxide-derived cocatalysts onto Cu2O/Ga2O3/TiO2 photocathodes to extend operating stability beyond 44 hours. Blocker: Requires wet-lab materials synthesis, atomic layer deposition, electrodeposition equipment, and photoelectrochemical testing apparatus.
Surface and Electrolyte Engineering on Semiconductor Electrodes for solar-assisted CO2 Reduction · EPFL
Left open
Investigate co-doping strategies in spray-pyrolysis-deposited iron oxide thin films to enhance photocatalytic activity. Blocker: Requires a wet chemistry and material synthesis lab with spray pyrolysis apparatus to synthesize and test thin films.
Elaboration and optimization of Iron Oxide thin films deposited via spray pyrolysis. Applications in water treatment · DSpace at University of El Oued
Left open
Synthesize dilute PdAu RCT catalysts on alternative metal oxide frameworks and evaluate support effects on catalytic oxidation performance. Blocker: Requires wet-lab chemical synthesis of alternative metal oxide supports and flow-reactor catalyst testing apparatus.
Oxidation Catalysis by Novel Dilute Palladium-in-Gold Nanoparticles Supported on Porous Silica · Harvard
Left open
Functionalize graphene field-effect transistors with metal oxide nanoparticles, metalloporphyrins, and bio-receptors for gas-phase volatile organic compound sensing. Blocker: Requires a wet chemistry and nanomaterials fabrication laboratory to synthesize functional materials and measure sensor responses.
Graphene-based Biochemical Sensing Array: Materials, System Design and Data Processing · MIT
Left open
Investigate the relationship between dielectric constant and bimolecular recombination rates across various metal oxide semiconductors. Blocker: Requires experimental transient absorption spectroscopy measurements across multiple metal oxide materials.
Time-resolved spectroscopic studies of SrTiO3 photocatalysts for water splitting · Imperial
Left open
Quantify nitric oxide interference on optical dissolved oxygen sensors and determine the underlying biophysical mechanism through laboratory testing. Blocker: Requires wet lab equipment, optical DO sensors, and controlled nitric oxide gas delivery systems.
Intensification of Biological Nutrient Removal Processes · Virginia Tech
Left open
Design and engineer self-assembled monolayer to transparent conducting oxide covalent bonding to improve perovskite solar cell moisture durability. Blocker: Requires wet lab chemical synthesis and experimental photovoltaic device fabrication and testing
MICROSTRUCTURE MODULATION FOR EFFICIENT CHARGE TRANSPORT IN PEROVSKITE SOLAR CELLS · Cornell
Left open
Determine the composition and crystal structure of evolved mixed oxide phases formed during redox cycling of perovskite thin films. Blocker: Requires a wet lab, ALD synthesis tools, physical redox reactors, and advanced characterization instruments (XRD, TEM, XPS).
Left open
Incorporate reduced graphene oxide interlayers or dopants like C60F48 or CuI into AACVD CuSCN perovskite solar cells to decrease series resistance. Blocker: Requires a physical materials synthesis and wet chemistry laboratory with AACVD equipment and solar cell fabrication tools.
Left open
Investigate electron-beam induced exsolution and re-oxidation reversibility of exsolved nanoparticles on lanthanum nickel oxide double perovskites. Blocker: Requires transmission electron microscopy (TEM) facilities and physical perovskite samples.
Lanthanum nickel oxide based double perovskites and their exsolution phenomena · Imperial
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