NOVELTY - The apparatus comprises: a semiconductor photoanode comprising macroscopic electric conducting material coated in part by nanoscopic conduction material; a cathode comprising macroscopic electric conducting material coated in part by nanoscopic conduction material; an element to switch the operation of hydrogen gas production from water vapor in the ambient air humidity to convert hydrogen into electricity; and an illumination intensity controller. The photoanode is positioned to receive light and ambient air. The photoanode and cathode are conductively interconnected for electron flow.    USE - The apparatus is useful for hydrogen production from ambient air humidity and light and for transformation of the generated hydrogen into electricity, and useful in a vehicle consisting of car, truck, train, buss, aircraft, spacecraft and off-road vehicles (all claimed).    ADVANTAGE - The apparatus enables efficient production of hydrogen from ambient air humidity and light, at low partial pressure below the lower explosion limit, without any water oxidation co-catalyst such as iridium ruthenium oxide (IrRuOx), and has lightweight.    DETAILED DESCRIPTION - The apparatus comprises: a semiconductor photoanode comprising macroscopic electric conducting material coated in part by nanoscopic conduction material; a cathode comprising macroscopic electric conducting material coated in part by nanoscopic conduction material; an element to switch the operation of hydrogen gas production from water vapor in the ambient air humidity to convert hydrogen into electricity; and an illumination intensity controller. The photoanode is positioned to receive light and ambient air. The photoanode and cathode are conductively interconnected for electron flow and separated by a proton exchange membrane or a membrane electrode assembly comprising proton exchange membrane for the proton flow to the cathode. The water vapor contained in a gas mixture comprising molecular oxygen provides the hydrogen atoms for hydrogen gas production, and the photoanode is illuminated by sunlight. The illumination controller is a filter to filter out visible and infrared light; or a switch (illumination/non-illumination switch) to let follow in succession periods of illumination of the semiconductor photoanode with periods of non-illumination (darkness) of the semiconductor photoanode. The membrane electrode assembly comprises hygroscopic nanoparticle aggregates. The nanoscopic electric conducting material of the photoanode is entirely coated with semiconductor oxide layer. The coating nano layer has a thickness of 3-15 nm. The nanoscopic electric conducting material comprises multiwall carbon nanotubes. The carbon nanotubes at the photoanode are coated with a continuous layer of semiconductor. The plasmonic nanoparticles, preferably silver-gold alloy nanoparticles are deposited on the continuous layer of semiconductor at the photoanode. The catalytic nano size platinum particles are deposited on the nanoscopic electric conducting material of the cathode. The membrane-electrode assembly is mounted in a two-compartment photoelectrochemical cell. The cathode compartment is closed to accumulate the produced hydrogen, and is left open or is foreseen from an inlet and outlet to purge with inert gas to transport and collect the produced hydrogen. The illumination controller is configured to control or reduce dehydration of the membrane electrode assembly or the proton exchange membrane and/or to control or reduce heating up of the semiconductor photoanode. An INDEPENDENT CLAIM is included for a method of operating the apparatus.