Chemical Bias Research Articles

(Invited) Photoelectrochemical Hydrogen Generation Derived from Water Dissociation Under Supercontinuum Solar Light (25)

We created a two-compartment cell (2CC) separated by a bipolar membrane (BPM1) sandwiched between through-holed electrodes (THEs) assembly (BPMTHEA-2CC) based on the Golden Role for sustainable water splitting derived from water dissociation (WD) with a dual chemical bias (CB).2-4 The BPMTHEA-2CC provides an infinite supply of active reaction species, H+ and OH-, from water with an opposite bidirectional charge separation under appropriate applied voltage conditions. We have achieved hydrogen generation derived from WD with BPMTHEA-2CC using an oxygen evolving reaction active TH dimensionally stable anode (De Nora Permelec Ltd) prepared on Pt gauze. Liberated gas was analyzed using a gas chromatograph equipped with a MS-5A column and a thermal conductive detector (TCD). We succeeded in detecting appropriate amounts of molecular hydrogen generated in the cathode of a large-sized BPMTHEA-2CC, anolyte (water)|TH anode|BPM|TH cathode|catholyte (water), by imposing a voltage with less than the theoretical 1.23 V for water splitting at room temperature. We disprove the theory of water electrolysis established for hundreds of years. However, we still require external voltage for water electrolysis. Instead of external voltage, we have harnessed supercontinuum solar light throughout by designing optical tandem, wavelength multiplexing. Zero-bias photocurrent was observed by applying TH n-type semiconductor photoanodes to BPMTHEA-2CC. WD at the junction of BPM is considered to be originated in second Wien effect. Thus Au nanoparticle (Au-NP) was introduced into the junction of BPM to carry out plasmon-induced (PI) WD. With mixing different sizes of Au NPs, a wide range of absorption wavelengths would be attainable. Preliminary results obtained using Au-NP modified BPMTHEA-2CC were reported with two plausible mechanisms.3 A simple 4-port chamber has been developed to measure hydrogen concentrations down to 7.5 ppm and was used to demonstrate PEC zero bias hydrogen generation with harnessing supercontinuum solar light. V. J. Frilette, J. Phys. Chem., 60, 435 (1956).K. Sakamaki et al., AST2019, June 2-5, 2019, Awaji Yumebutai, Japan, O-24 (2019).K. Sakamaki et al., 236th ECS Meeting, Oct. 13-17, 2019, Atlanta, GA, USA, I04-1896 (2019).K. Sakamaki et al., J. Applied Electrochem. 49, 949-962 (2019). https://doi.org/10.1007/s10800-019-01337-8 Figure 1

Photoelectrochemical Supercontinuum Solar Light Zero Bias Hydrogen Generation with Membrane-Based Cells Designed for Decreasing Overall Water Electrolysis Voltage and Water Dissociation (23)

We have created a two-compartment cell (2CC) separated by a bipolar membrane (BPM1) sandwiched between through-holed electrodes (THEs) assembly (BPMTHEA-2CC) based on the Golden Role for sustainable water splitting derived from water dissociation (WD) with a dual chemical bias (CB).2 The BPMTHEA-2CC has distinguishing characteristics of integrated functionality of dualities, providing an infinite supply of active reaction species, H+ and OH-, from water with an opposite bidirectional charge separation under appropriate applied voltage conditions. We wish to suggest the feasibility of electrochemical water splitting (decomposition) with less than theoretical 1.23 V at RT using an anolyte (water or base)|OER active THE|BPM|HER active THE|catholyte (water or acid). We disprove the theory of water electrolysis established for hundreds of years with sustainable dual CBs. However, we still require external voltage for water electrolysis. Instead of external voltage, we have harnessed solar energy by applying the TH n-type semiconductor photoanodes to BPMTHEA-2CC for a zero-bias photogalvanic cell. Anatase TH TiO2 was used for a model to demonstrate our concept. We succeeded in measuring photocurrent from distilled water with a response of optical shutter. The magnitude of the zero bias photocurrent is proportional to the magnitude of outer CB and illuminance intensity. TH Fe2O3 was prepared by the aqueous chemical growth method. Visible light zero bias photocurrent from distilled water was also observed in the TH Fe2O3 photogalvanic cell without any external voltage. Currently, our research efforts are focused on PEC zero bias hydrogen generation with harnessing supercontinuum solar light by designing optical tandem, wavelength multiplexing with BPMTHEA-2CC and Au plasmon-induced WD. 1) V. J. Frilette, J. Phys. Chem., 60, 435 (1956).2) K. Sakamaki et al., 97th CSJ, 3A6-05 (2017), 68th ISE, Providence, USA, ise171503 (2017), The 22nd Top. Meeting of ISE, Tokyo, abs170627 (2018), 69th ISE, Bologna, Italy, ise183543 (2018). Figure 1

Photoelectrochemical visible light zero-bias hydrogen generation with membrane-based cells designed for decreasing overall water electrolysis voltage and water dissociation: the second stage

We created a two-compartment cell (2CC) separated by a bipolar membrane (BPM) sandwiched between a through-holed (TH) electrode assembly (BPMTHEA-2CC) with the distinguishing feature of integrated functionality of dualities based on the Golden Rule for sustainable water splitting derived from water dissociation (WD) with a dual chemical bias (CB). A decisive advantage of this system is that all electrolytes used are sustainable because the reaction starts from WD. The opposite bidirectional charge separation of H+ and OH− ions derived from WD generates inner CB within BPM. Many anolyte–catholyte combinations are possible in BPMTHEA-2CC, which induces outer CB (OCB). Therefore, dual CB reduces overall water electrolysis voltage. We have achieved hydrogen generation derived from WD with BPMTHEA-2CC using an oxygen evolving reaction active TH dimensionally stable anode by imposing a voltage with less than the theoretical 1.23 V for water splitting at room temperature. We disprove the theory of water electrolysis established for hundreds of years. Instead of external voltage, we have harnessed solar energy by applying the TH n-type semiconductor photoanodes to BPMTHEA-2CC for a zero-bias photogalvanic cell. Anatase TH TiO2 was used for a model to demonstrate our concept. We succeeded in measuring photocurrent from distilled water with a response of optical shutter. The magnitude of the zero-bias photocurrent is proportional to the magnitude of OCB and illuminance intensity. TH Fe2O3 was prepared by the aqueous chemical growth method. Visible light zero-bias photocurrent from distilled water was also observed in the TH Fe2O3 photogalvanic cell without any external voltage.