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Fundamental (Photo)electrocatalysis
Areas
Areas
Energy Conversion & Storage
Biochemical Direct Air CO2 Capture
[Fundamental (photo)electrocatalysis]
[Fundamental (photo)electrocatalysis]
Polarization decoupling for controlling electrochemical selectivity (emulating biological ET)
The diode-like behavior of semiconductor-liquid junctions provide a way for current and applied potential to be functionally decoupled in electrochemical devices. This enables investigations of how independent modulation of current and applied potential impacts electrochemical reactivity and selectivity. A biased electrolyzer incorporating a photoelectrochemical counter electrode can drive a specified reaction of interest, with the light intensity incident on the photoelectrode limiting the total cell current. Continuous variation of incident light intensity (by means such as a variable neutral density filter between the photoelectrode and light source), generates a continuum of light-dependent, electrochemical polarization curves that may now be accessed. Here, the ability to vary electron energy by biasing the cell across a range of potentials (with a potentiostat), while independently limiting the total current by controlling the photoelectrode's illumination intensity, yields a case where current and applied potential are effectively decoupled. This enables systematic exploration of the effects of independently changing reaction energetics (applied voltage) and limiting electrochemical kinetics (current) for reactions where multiple reaction pathways (and multiple products, as seen in CO2 reduction) are possible.
https://pubs.acs.org/doi/full/10.1021/acs.jpclett.3c03051
https://iopscience.iop.org/article/10.1088/1361-6463/ad6008/meta
Electronic tunnel junctions & time-domain polarization for steering electrochemical selectivity (emulating biological ET)
Most chemical processes occur with characteristic timescales, set by the inverse rate of reaction. Timing the confluence of substrate and electrons at an active site can be achieved by introducing time as an degree of freedom in catalysis. By definition, this is impossible when reactions are run at steady-state (time-invariant) - the case of most chemical reactions. However, transient operation of chemical processes introduces an explicit time dependence in reactivity. In this project, we exploit transient operation through the use of RC circuits as a strategy for enabling time-dependent control of electrochemical reactivity. The additional incorporation of tunnel junctions allow for the regulation of electron transfer rates independent of applied potential by changing tunnel barrier width. This provides an additional degree of freedom for controlling electrochemical reactivity.
Sequenced cascade catalysis (mimicking biochemical cascades)
Projects here investigate new cell prototypes and the fundamental chemical physics of cascade CO2 electrolysis. CO2 conversion to C2 or greater products is achieved through conversion of CO2 to CO on an Au or Ag catalyst, followed by CO upgrading to C2+ products. Device-level efforts explore a new architecture for cascade catalysis, where directional flow enforces a sequential path for substrate movement through the cell, rather than allowing free diffusion between catalyst layers. This work explores whether this type of enforced, sequential flow can improve product conversion efficiencies and CO2 utilization in CO2 reduction.
related: https://chemrxiv.org/engage/chemrxiv/article-details/67c3a55c81d2151a02a86017;
https://pubs.rsc.org/en/content/articlelanding/2025/sc/d5sc02781k
Tafel fitting algorithms
How can Tafel analysis be used to determine catalyst activities quantitatively, as opposed to the qualitative guesswork it usually requires? This work emerged from a hypothesis that it may be possible to rigorously fit Tafel data by applying some set of constraints linking a Tafel plot to its corresponding J-V polarization curve. We validate this approach by pairing theory with experiment, benchmarking the algorithm against experimental data for three distinct, canonical electrochemical reactions: platinum-catalyzed hydrogen evolution, iridium-catalyzed oxygen evolution, and platinum-catalyzed dioxygen reduction. In each case, the algorithm predicts the same Tafel slope as those reported in long-established bodies of electrochemical literature. The procedure should significantly improve the ability of researchers to accurately rate and compare electrocatalyst materials.
Charge carrier dispersion and electrochemical selectivity
Traditionally, streams of charge originating from donor surfaces giving rise to electrochemical currents are treated as homogeneous, implying microscopic interchangeability between the individual electrons or holes forming an electrochemical oxidation or reduction current. However, accounting for the fact that donor/acceptor states in bulk metal catalysts will span an energy continuum, rather than forming discrete orbital states of a single energy, imply that electrochemical currents are in fact streams of carriers assuming a spectrum of energies, with the relative contributions of carriers of a particular energy being a consequence of the donor band’s Fermi-Dirac distribution and energy-weighted density of states. This interpretation is directly implied by the form of the Marcus-Hush-Chidsey (MHC) integral, a model used that applies the original Marcus description of inner-sphere electron transfers to electrode kinetics through an explicit inclusion of non-degenerate metal donor states. In this work, application of the MHC model explores how understanding currents as heterogeneous streams of electronic carriers may improve our understanding of the catalytic promiscuity observed in many electrochemical processes.
Information entropy in electrochemical selectivity
This work tries to understand what is required to control bifurcations in chemical reactivity, the extent to which these bifurcations are determined by the level of specificity used to specify the initial reactant state. This work will quantify degrees of control over the reactant state as how much information is required to specify the properties of a reactant pool to yield some unique product distribution, using entropy definitions detailed by Claude Shannon's information theory. In this application of information theory, product distribution states are understood as comprising one of many possible product microstates that an initial reactant pool may access over the course of CO2 reduction (or other reactions with multiple possible end products). Highly selective reactions represent cases of being able to target just one of several statistically possible microstates, while promiscuous reactions access many such microstates over the course of reaction time. Viewed this way, the problem of chemical selectivity reduces to a subset of the general problem of information transfer. We expect this framing to usefully augment our current understanding of the factors determining electrochemical selectivity.
[Energy conversion & storage]
[Energy conversion & storage]
Dark CO2 and hydrogen electrolyzers
Our work scope extends to applied research on the durability testing of electrolyzers for CO, syngas and hydrogen evolution.
Integrated photoelectrochemical devices (Artificial Photosynthesis)
This work aims to address a standing challenge in the field of photoelectrochemistry: how may catalysts and catalyst supports developed for dark electrochemistry be integrated with wireless, photoelectrochemical (PEC) devices? This project considers a device architecture offering a potential answer to this problem, as it enables the incorporation of carbon-supported, dark catalysts in a wireless, light-compatible scheme. The ability to integrate robust, dark catalysts with light-driven PEC cells significantly expands the universe of catalysts that may be considered for use in wireless, integrated PEC devices, without having to make the typical trade-offs between device transparency and catalytic activity or stability.
https://iopscience.iop.org/article/10.1149/MA2020-01391775mtgabs/meta
https://pubs.rsc.org/en/content/articlelanding/2022/ee/d1ee03957a/unauth
https://iopscience.iop.org/article/10.1149/2.1151913jes/meta
https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/aenm.202100070
Recirculation systems for concentrating CO2 electrolyzer products
Faradaic efficiencies near 100% have been achieved for certain CO2 reduction products such as CO, but the electrolyzer fuel streams usually contain large fractions of unreacted CO2, resulting in suboptimal product concentrations. The system we've developed recycles unreacted CO2, along with the products generated on a single pass, pumping them back into the CO2 reduction reactor. This allows for product concentrations to accumulate in the fuel stream, while driving higher CO2 conversion rates.
https://pubs.rsc.org/en/content/articlelanding/2024/se/d3se01506h/unauth
Evaluating time-dependent efficiency fluctuations in PEC devices
Performance drops in PEC device functioning are manifested through reductions in the resulting electrical current, along with reductions in the solar-to-fuel conversion efficiency. However, assigning the causes for these drops, which will typically fall into either one of two types (electrochemical or photovoltaic losses) is not a straightforward task. Our work on PEC devices resulted in a new methodology for decomposing PEC performance losses into their constituent electrochemical and photophysical contributions.
https://pubs.aip.org/aip/apm/article/8/3/031107/1064401
https://pubs.rsc.org/en/content/articlelanding/2022/ee/d1ee03957a/unauth
https://github.com/MEG-LBNL/Current-Voltage-Analysis-Tool-for-Solar-Fuel-Production-CATS
Autocatalytic fuel cycles (PCR mimicry)
This work advances a framework for practical, electrochemical fuel generation displaying exponential product yields and product formation rates as functions of time. Exponential reaction scaling for formate/formic acid replication is realized through an autocatalytic cycle that emulates the process of DNA replication facilitated by the well-known polymerase chain reaction (PCR). In this replication case, an initial buildup of formate into a two-carbon chain through CO2 carboxylation forms oxalate. A subsequent, two-electron reduction yields glyoxylate, with base-mediated hydrolysis driving C-C bond fission of glyoxylate into two molecules of formate. These products are then recycled back to serve as reactants. Each step of the proposed fuel cycle shows direct analogy to the steps of DNA annealing, nucleotide polymerization and hybridized strand fission that are responsible for the exponential product yields observed in PCR-mediated DNA synthesis.
Nuclear chemical conversions for fuel synthesis and CO2 capture
The high energy content of the radioemissions from such materials (several MeV per particle) far exceed the energies required for converting CO2 to CO2·- (-2.9 V vs NHE), a key intermediate in several CO2 conversion pathways to valorized products, such as fuels and feedstocks. This project uses stochastic simulations to explore the use of ionizing radiation from nuclear waste products, such as Strontium 90 and Cesium 137, as pump sources for driving the conversion of CO2 to oxalate. Oxalate can serve as both a high-density CO2 sequestration sink and facile precursor for chemical fuels such as hydrogen and formate. In addition, these investigations will be folded into the broader effort towards the design of autocatalytic cycles for rapid fuel synthesis through PCR-type replication (above), with nuclear decays driving key radical chemistries for the proposed fuel cycle.
a) H2O + rad → [H2O*] → H2O+ + e-(aq)
b) CO2 + e-(aq) → CO2-
c) 2 CO2- → C2O42-
[Biochemical direct air CO2 capture]
[Biochemical direct air CO2 capture]
Genetically engineering cyanobacterial surface display of carbonic anhydrases (CyCAMs)
The ability of carbonic anhydrase (CA) metalloenzymes to catalyze the otherwise slow hydration of CO2 into carbonic acid (H2CO3) makes them useful CO2 hydration catalysts, with applications in a wide range of CO2 capture strategies. However, a key bottleneck towards scaled implementation of enzymatic CO2 capture involves the cost of sourcing the CA in sufficient quantities However, as a biosynthetic product, CA can be sourced renewably by using a photosynthetic bacterial expression system, engineered to produce the enzyme during the course of cellular photometabolism. Towards this goal, we've engineered genetically-modified cyanobacterial strains growing on sunlight and CO2, as a “factories” for renewably generating carbonic anhydrase by expressing it on the cell exterior.
https://doi.org/10.26434/chemrxiv-2025-0rnx8
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