Ge Zhang

All Publications

• Seawater alkalization via an energy-efficient electrochemical process for CO2 capture. Proceedings of the National Academy of Sciences of the United States of America Guan, X., Zhang, G., Li, J., Kim, S. C., Feng, G., Li, Y., Cui, T., Brest, A., Cui, Y. 2024; 121 (45): e2410841121

  Abstract

  Electrochemical pH-swing strategies offer a promising avenue for cost-effective and energy-efficient carbon dioxide (CO2) capture, surpassing the traditional thermally activated processes and humidity-sensitive techniques. The concept of elevating seawater's alkalinity for scalable CO2 capture without introducing additional chemical as reactant is particularly intriguing due to its minimal environmental impact. However, current commercial plants like chlor-alkali process or water electrolysis demand high thermodynamic voltages of 2.2 V and 1.23 V, respectively, for the production of sodium hydroxide (NaOH) from seawater. These high voltages are attributed to the asymmetric electrochemical reactions, where two completely different reactions take place at the anode and cathode. Here, we developed a symmetric electrochemical system for seawater alkalization based on a highly reversible and identical reaction taking place at the anode and cathode. We utilize hydrogen evolution reaction at the cathode, where the generated hydrogen is looped to the anode for hydrogen oxidation reaction. Theoretical calculations indicate an impressively low energy requirement ranging from 0.07 to 0.53 kWh/kg NaOH for established pH differences of 1.7 to 13.4. Experimentally, we achieved the alkalization with an energy consumption of 0.63 kWh/kg NaOH, which is only 38% of the theoretical energy requirements of the chlor-alkali process (1.64 kWh/kg NaOH). Further tests demonstrated the system's potential of enduring high current densities (~20 mA/cm2) and operating stability over an extended period (>110 h), showing its potential for future applications. Notably, the CO2 adsorption tests performed with alkalized seawater exhibited remarkably improved CO2 capture dictated by the production of hydroxide compared to the pristine seawater.

  View details for DOI 10.1073/pnas.2410841121

  View details for PubMedID 39467125

• In situ formation of liquid crystal interphase in electrolytes with soft templating effects for aqueous dual-electrode-free batteries NATURE ENERGY Li, Y., Zheng, X., Carlson, E. Z., Xiao, X., Chi, X., Greenburg, L. C., Zhang, G., Zhang, E., Liu, C., Yang, Y., Kim, M., Feng, G., Zhang, P., Su, H., Guan, X., Zhou, J., Wu, Y., Xue, Z., Li, W., Bajdich, M., Cui, Y. 2024

  View details for DOI 10.1038/s41560-024-01638-z

  View details for Web of Science ID 001317361000002

• High energy density picoliter-scale zinc-air microbatteries for colloidal robotics SCIENCE ROBOTICS Zhang, G., Yang, S., Yang, J., Gonzalez-Medrano, D., Miskin, M. Z., Koman, V. B., Zeng, Y., Li, S., Kuehne, M., Liu, A., Brooks, A. M., Kumar, M., Strano, M. S. 2024; 9 (93): eade4642

  Abstract

  The recent interest in microscopic autonomous systems, including microrobots, colloidal state machines, and smart dust, has created a need for microscale energy storage and harvesting. However, macroscopic materials for energy storage have noted incompatibilities with microfabrication techniques, creating substantial challenges to realizing microscale energy systems. Here, we photolithographically patterned a microscale zinc/platinum/SU-8 system to generate the highest energy density microbattery at the picoliter (10-12 liter) scale. The device scavenges ambient or solution-dissolved oxygen for a zinc oxidation reaction, achieving an energy density ranging from 760 to 1070 watt-hours per liter at scales below 100 micrometers lateral and 2 micrometers thickness in size. The parallel nature of photolithography processes allows 10,000 devices per wafer to be released into solution as colloids with energy stored on board. Within a volume of only 2 picoliters each, these primary microbatteries can deliver open circuit voltages of 1.05 ± 0.12 volts, with total energies ranging from 5.5 ± 0.3 to 7.7 ± 1.0 microjoules and a maximum power near 2.7 nanowatts. We demonstrated that such systems can reliably power a micrometer-sized memristor circuit, providing access to nonvolatile memory. We also cycled power to drive the reversible bending of microscale bimorph actuators at 0.05 hertz for mechanical functions of colloidal robots. Additional capabilities, such as powering two distinct nanosensor types and a clock circuit, were also demonstrated. The high energy density, low volume, and simple configuration promise the mass fabrication and adoption of such picoliter zinc-air batteries for micrometer-scale, colloidal robotics with autonomous functions.

  View details for DOI 10.1126/scirobotics.ade4642

  View details for Web of Science ID 001293034500001

  View details for PubMedID 39141708

• Colloidal robotics. Nature materials Liu, A. T., Hempel, M., Yang, J. F., Brooks, A. M., Pervan, A., Koman, V. B., Zhang, G., Kozawa, D., Yang, S., Goldman, D. I., Miskin, M. Z., Richa, A. W., Randall, D., Murphey, T. D., Palacios, T., Strano, M. S. 2023

  Abstract

  Robots have components that work together to accomplish a task. Colloids are particles, usually less than 100m, that are small enough that they do not settle out of solution. Colloidal robots are particles capable of functions such as sensing, computation, communication, locomotion and energy management that are all controlled by the particle itself. Their design and synthesis is an emerging area of interdisciplinary research drawing from materials science, colloid science, self-assembly, robophysics and control theory. Many colloidal robot systems approach synthetic versions of biological cells in autonomy and may find ultimate utility in bringing these specialized functions to previously inaccessible locations. This Perspective examines the emerging literature and highlights certain design principles and strategies towards the realization of colloidal robots.

  View details for DOI 10.1038/s41563-023-01589-y

  View details for PubMedID 37620646

• Colloidal State Machines as Smart Tracers for Chemical Reactor Analysis ADVANCED INTELLIGENT SYSTEMS Zhang, G., Yang, J., Yang, S., Brooks, A. M., Koman, V. B., Gong, X., Strano, M. S. 2023

  View details for DOI 10.1002/aisy.202300130

  View details for Web of Science ID 001020024700001

• Synergistic multi-source ambient RF and thermal energy harvester for green IoT applications ENERGY REPORTS Bakytbekov, A., Nguyen, T. Q., Zhang, G., Strano, M. S., Salama, K. N., Shamim, A. 2023; 9: 1875-1885

  View details for DOI 10.1016/j.egyr.2023.01.027

  View details for Web of Science ID 000923091700001

• Investigations of Vacancy-Assisted Selective Detection of NO2 Molecules in Vertically Aligned SnS2. ACS sensors Kumar, A., Gutal, A. P., Sharma, N., Kumar, D., Zhang, G., Kim, H., Kumar, P., Paranjothy, M., Kumar, M., Strano, M. S. 2023; 8 (3): 1357-1367

  Abstract

  Two important methods for enhancing gas sensing performance are vacancy/defect and interlayer engineering. Tin sulfide (SnS2) has recently attracted much attention for sensing of the NO2 gas due to its active surface sites and tunable electronic structure. Herein, SnS2 has been synthesized by the chemical vapor deposition (CVD) method followed by nitrogen plasma treatment with different exposure times for fast detection of NO2 molecules. Plasma treatment created a substantial number of surface vacancies on SnS2 flakes, which were controlled by the exposure period to modify the surface of flakes. After 12 min of nitrogen plasma treatment, SnS2 nanoflakes show considerable improvement in NO2 sensing characteristics, including a high sensing response of 264% toward 100 ppm NO2 at 120°C. The enhancement in the relative response of the sensor is due to the electronic interaction between NO2 molecules and the S vacancies on the surface of SnS2. Density functional theory (DFT) computations indicate that the S-vacancy defects on the surface dominate the effective NO2 detection and the NO2 adsorption mechanism transition from physisorption to chemisorption. Adsorption kinetics of the NO2 gas over SnS2 nanoflake-based chemiresistor sensors were studied using the Lee and Strano model [ Langmuir 2005, 21(11), 5192-5196]. The irreversible rate of the reaction for various NO2 concentrations exposed to the gas sensor is extracted using this model, which also appropriately describes the response curves. The forward rate constant of the irreversible gas sensor increased with the increase of the N2 plasma treatment time and reached the maximum in the 12 min plasma-treated sample. Through defect engineering, this research may open up new vistas for the design and synthesis of 2D materials with enhanced sensing properties.

  View details for DOI 10.1021/acssensors.3c00133

  View details for PubMedID 36921259

• Emergent microrobotic oscillators via asymmetry-induced order NATURE COMMUNICATIONS Yang, J., Berrueta, T. A., Brooks, A. M., Liu, A., Zhang, G., Gonzalez-Medrano, D., Yang, S., Koman, V. B., Chvykov, P., LeMar, L. N., Miskin, M. Z., Murphey, T. D., Strano, M. S. 2022; 13 (1): 5734

  Abstract

  Spontaneous oscillations on the order of several hertz are the drivers of many crucial processes in nature. From bacterial swimming to mammal gaits, converting static energy inputs into slowly oscillating power is key to the autonomy of organisms across scales. However, the fabrication of slow micrometre-scale oscillators remains a major roadblock towards fully-autonomous microrobots. Here, we study a low-frequency oscillator that emerges from a collective of active microparticles at the air-liquid interface of a hydrogen peroxide drop. Their interactions transduce ambient chemical energy into periodic mechanical motion and on-board electrical currents. Surprisingly, these oscillations persist at larger ensemble sizes only when a particle with modified reactivity is added to intentionally break permutation symmetry. We explain such emergent order through the discovery of a thermodynamic mechanism for asymmetry-induced order. The on-board power harvested from the stabilised oscillations enables the use of electronic components, which we demonstrate by cyclically and synchronously driving a microrobotic arm. This work highlights a new strategy for achieving low-frequency oscillations at the microscale, paving the way for future microrobotic autonomy.

  View details for DOI 10.1038/s41467-022-33396-5

  View details for Web of Science ID 000868657300013

  View details for PubMedID 36229440

  View details for PubMedCentralID PMC9561614

• Memristor Circuits for Colloidal Robotics: Temporal Access to Memory, Sensing, and Actuation ADVANCED INTELLIGENT SYSTEMS Yang, J., Liu, A., Berrueta, T. A., Zhang, G., Brooks, A. M., Koman, V. B., Yang, S., Gong, X., Murphey, T. D., Strano, M. S. 2021

  View details for DOI 10.1002/aisy.202100205

  View details for Web of Science ID 000733375600001

• Solvent-induced electrochemistry at an electrically asymmetric carbon Janus particle. Nature communications Liu, A. T., Kunai, Y., Cottrill, A. L., Kaplan, A., Zhang, G., Kim, H., Mollah, R. S., Eatmon, Y. L., Strano, M. S. 2021; 12 (1): 3415

  Abstract

  Chemical doping through heteroatom substitution is often used to control the Fermi level of semiconductor materials. Doping also occurs when surface adsorbed molecules modify the Fermi level of low dimensional materials such as carbon nanotubes. A gradient in dopant concentration, and hence the chemical potential, across such a material generates usable electrical current. This opens up the possibility of creating asymmetric catalytic particles capable of generating voltage from a surrounding solvent that imposes such a gradient, enabling electrochemical transformations. In this work, we report that symmetry-broken carbon particles comprised of high surface area single-walled carbon nanotube networks can effectively convert exothermic solvent adsorption into usable electrical potential, turning over electrochemical redox processes in situ with no external power supply. The results from ferrocene oxidation and the selective electro-oxidation of alcohols underscore the potential of solvent powered electrocatalytic particles to extend electrochemical transformation to various environments.

  View details for DOI 10.1038/s41467-021-23038-7

  View details for PubMedID 34099639