Photochemical energy conversion is more efficient when a single light-absorbing unit is split into multiple light-absorbing units (N) that are each 1/N as thick as the single light-absorbing unit and thus use the same amount of material as the single light-absorbing unit. For electrocatalytic parameters relevant to water electrolysis, the maximum efficiency for solar-to-fuel conversion from a 1.75 eV bandgap material increases from approximately 1% for a single light-absorbing unit to greater than 20% for 128 identical stacked light-absorbing units. Alterations in utilization of photons results in a better match of the light-absorber power output to the load of the chemical transformation and in the case of high-quality light-absorbers there is an added benefit from radiative coupling between the light-absorbing units via photon recycling.

Photochemical energy conversion is more efficient when a single light-absorbing unit is split into multiple light-absorbing units (N) that are each 1/N as thick as the single light-absorbing unit and thus use the same amount of material as the single light-absorbing unit. For electrocatalytic parameters relevant to water electrolysis, the maximum efficiency for solar-to-fuel conversion from a 1.75 eV bandgap material increases from approximately 1% for a single light-absorbing unit to greater than 20% for 128 identical stacked light-absorbing units. Alterations in utilization of photons results in a better match of the light-absorber power output to the load of the chemical transformation and in the case of high-quality light-absorbers there is an added benefit from radiative coupling between the light-absorbing units via photon recycling.

Photochemical energy conversion is more efficient when a single light-absorbing unit is split into multiple light-absorbing units (N) that are each 1/N as thick as the single light-absorbing unit and thus use the same amount of material as the single light-absorbing unit. For electrocatalytic parameters relevant to water electrolysis, the maximum efficiency for solar-to-fuel conversion from a 1.75 eV bandgap material increases from approximately 1% for a single light-absorbing unit to greater than 20% for 128 identical stacked light-absorbing units. Alterations in utilization of photons results in a better match of the light-absorber power output to the load of the chemical transformation and in the case of high-quality light-absorbers there is an added benefit from radiative coupling between the light-absorbing units via photon recycling.

Provided is a semiconductor photoelectrode that exhibits a catalytic function with light irradiation to cause an oxidation-reduction reaction. The semiconductor photoelectrode includes: a conductive or insulating substrate; a semiconductor thin film disposed on the surface of the substrate; a catalyst layer disposed on the surface of the semiconductor thin film; a light transmission layer disposed in a lattice shape on the surface of the catalyst layer; and a protective layer disposed to cover the rear surface of the substrate and the side surfaces of the substrate and the semiconductor thin film. The semiconductor photoelectrode having another configuration includes a second semiconductor thin film disposed between the semiconductor thin film and the catalyst layer.

Provided is a semiconductor photoelectrode that exhibits a catalytic function with light irradiation to cause an oxidation-reduction reaction. The semiconductor photoelectrode includes: a conductive or insulating substrate; a semiconductor thin film disposed on the surface of the substrate; a catalyst layer disposed on the surface of the semiconductor thin film; a light transmission layer disposed in a lattice shape on the surface of the catalyst layer; and a protective layer disposed to cover the rear surface of the substrate and the side surfaces of the substrate and the semiconductor thin film. The semiconductor photoelectrode having another configuration includes a second semiconductor thin film disposed between the semiconductor thin film and the catalyst layer.

A gas phase reduction device for carbon dioxide is a gas phase reduction device for carbon dioxide that exerts a catalytic function by light irradiation to generate oxidation-reduction reaction. The gas phase reduction device includes an oxidation tank in which an aqueous solution is put, a reduction tank to which carbon dioxide is supplied, a semiconductor photoelectrode installed in the aqueous solution, and a porous electrode-supported electrolyte membrane that is a joint body of an electrolyte membrane and a porous reduction electrode, the porous electrode-supported electrolyte membrane being installed between the oxidation tank and the reduction tank with the electrolyte membrane facing the oxidation tank and the porous reduction electrode facing the reduction tank. Voltage between a reference electrode installed in the aqueous solution and a reference electrode installed in contact with the electrolyte membrane is measured by a voltmeter, and a control unit increases voltage between the semiconductor photoelectrode and the porous reduction electrode in accordance with change in voltage between the reference electrodes from an initial value at start of reaction. The control unit includes a solar cell and a constant voltage power supply, and the solar cell is arranged on an extension line of a straight line from a light source toward the semiconductor photoelectrode, and generates power utilizing light emitted to and transmitted through the semiconductor photoelectrode.

A gas phase reduction device for carbon dioxide is a gas phase reduction device for carbon dioxide that exerts a catalytic function by light irradiation to generate oxidation-reduction reaction. The gas phase reduction device includes an oxidation tank in which an aqueous solution is put, a reduction tank to which carbon dioxide is supplied, a semiconductor photoelectrode installed in the aqueous solution, and a porous electrode-supported electrolyte membrane that is a joint body of an electrolyte membrane and a porous reduction electrode, the porous electrode-supported electrolyte membrane being installed between the oxidation tank and the reduction tank with the electrolyte membrane facing the oxidation tank and the porous reduction electrode facing the reduction tank. Voltage between a reference electrode installed in the aqueous solution and a reference electrode installed in contact with the electrolyte membrane is measured by a voltmeter, and a control unit increases voltage between the semiconductor photoelectrode and the porous reduction electrode in accordance with change in voltage between the reference electrodes from an initial value at start of reaction. The control unit includes a solar cell and a constant voltage power supply, and the solar cell is arranged on an extension line of a straight line from a light source toward the semiconductor photoelectrode, and generates power utilizing light emitted to and transmitted through the semiconductor photoelectrode.

An electrolyser (F) for generating hydrogen from water, the electrolyser comprising an electrode (102), the electrode (120) comprising nanoparticles selected from Group 1 nanoparticles or alloys or composites or mixtures thereof.

An electrolyser (F) for generating hydrogen from water, the electrolyser comprising an electrode (102), the electrode (120) comprising nanoparticles selected from Group 1 nanoparticles or alloys or composites or mixtures thereof.

Described herein are devices and methods utilizing cascade photocatalysis to drive multiple chemical reactions via a series of photoelectrochemical catalysts driven by the conversion of light into current by one or more photovoltaic devices. The described devices and methods are tunable and may be used in conjunction with different reactants and products, including the conversion of carbon dioxide into valuable hydrocarbon products.