Electrochemical interfaces for energy, biology, and environment

The Liu group at UCLA develops electrochemistry-enabled microenvironments for catalysis and microbiology. Combining the expertise in electrochemistry, nanomaterials and machine learning, the Liu group has three unique research thrusts under such as an overarching theme: (1) Design the extracellular microenvironments and materials-microorganism interfaces for biocatalysis and microbiology; (2) Develop catalytic systems with microscopic spatial control using electrochemistry and nanomaterials; (3) Applying machine-learning (ML) and artificial intelligence (AI) in electrochemistry and nanomaterials. As described below, those three multidisciplinary thrusts are synergistically interconnected, highlighting the interdisciplinary nature of the Liu group.

Research Thrust 1: Design the extracellular microenvironments and materials-microorganism interfaces for biocatalysis and microbiology.
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One research focus in the Liu group is the investigation and design of microenvironments, through electrochemistry and materials, to mimic natural microbial habitats, enable new studies in microbiology, and facilitate efficient biocatalysis powered by renewable energy. The microbial exchange of energy and matter with their immediate surroundings, the microenvironments, is critical to microbial metabolisms and regulations in environment, energy, and biomedical applications. At UCLA, the Liu group designs advanced bio-abiotic interface in order to facilitate the reaction of electricity-driven microbial fixation of CO2 and N2, and provide a comprehensive picture about the interplay between materials and microbiology, with characterizations of materials science and microbiology, in different scenarios of bio-based chemical transformations. Moreover, the Liu group employs nanomaterials and electrochemistry to spatiotemporally control the extracellular space in microbiology. We developed biocompatible electrochemical platforms that spatially and temporally modulate the concentration profiles of biologically important  small molecules such as O2 and reactive oxygen species (ROS). We envision that our electrochemistry-enabled spatiotemporal control of extracellular space not only mimics the natural microbial habitats but also serves as a quantifiable perturbation towards the microbial ensemble. Such platforms will offer valuable information about the dynamic response and spatial propagation of collective behaviors in diverse microbial communities.

Research Thrust 2: Develop catalytic systems with microscopic spatial control using electrochemistry and nanomaterials. More details

In line with the concept of controlling microenvironments for microbiology in Thrust 1, the Liu group also envisions to electrochemically create microenvironments and establish new catalytic cycles seemingly impossible in solution. We hypothesize that we can expand the design space of catalysis by utilizing microscopic concentration gradients, for example microenvironments generated by electrochemistry and nanomaterials, to establish solution catalysis impossible in homogeneous solution. For example, we demonstrated a new solution catalytic cycle of ambient CH4-to-CH3OH conversion with O2 as oxidant, which utilizes O2-deactivating, CH4-activating Rh(II) metalloradiacls for O2-based CH4 oxidation into CH3OH. The nanowire array of electrochemical O2 reduction creates a microscopic O2-free domain within the wire array, and effectively establishes a compartmentalized “mini-glovebox” in air that allows diffusion and the synchronization of aerobic and anaerobic steps into a complete catalytic cycle. Furthermore, we generalized this concept and established a design principle based on a general kinetic model of organometallic catalysis. We reported a set of conditions under which spatially controlled organometallic catalysis or compartmentalized ones will be advantageous. Our work reminds the community that compartmentalization or spatial control of catalysis is not necessarily a panacea for all applications in organometallics, hence paving the road towards a rational design of spatially controlled organometallic reactions.

Research Thrust 3: Applying machine-learning (ML)  and artificial intelligence (AI) in electrochemistry and nanomaterials. More details

A fledging research thrust in the Liu group is the use of ML and AI to address the challenges not only synergistically in our aforementioned research areas but also in the general field of electrochemistry and nanomaterials. We envision that a wider application of our electrochemically generated microenvironments (Thrust 1 and 2) requires a fast ML-based inverse design towards the physical and chemical properties of electrochemical nanomaterials, in order to satisfy the diverse and varying scenarios of microenvironments in microbiology and catalysis. We are also actively developing is the use of AI to automatically analyze electrochemical data such as cyclic voltammograms in the context of fully automated electrochemical research. We believe ML and AI will transform how we conduct research in the field of electrochemistry and nanomaterials, for a myriad of applications in energy, environment, and biology.