Abstract: Aiming at the scientific and technical issues of low hydrogen production efficiency and microgravity environmental adaptation faced by extraterrestrial water splitting，this study adopts an innovative approach of photosynthesis to optimize the hydrogen evolution reaction and gas-liquid separation process.To solve the problems of traditional noble metal-based catalysts，such as high cost and difficult to fabricate ideal micro- and nano- structured electrodes，an ultrathin two-dimensional mesh structure of cobalt phosphide/cobalt hydroxide（CoPOH）composite catalyst was designed and prepared.The overpotential of the composite catalyst was only 12mV and the Tafel slope was only 61.2mV/dec at a current density of 10mA/cm2，and the overpotential of the composite catalyst only increased 26mV after 1000 cycles of cyclic voltammetry testing，indicating that the composite catalyst can effectively improve the hydrogen production rate and energy conversion efficiency as well as outstanding stability.Furthermore，using the projection microstereolithography（PμSL）3D printing technique and mimicking the superhydrophobic surface of the legs of water striders，a kind of Janus functional interface was successfully prepared.The interface enabled different kinds of gases to pass quickly in the opposite direction to gravity，and the time for a bubble to pass through the membrane was about 2.4ms.Based on the excellent gas-liquid separation characteristics of this interface，a functional device for hydrogen production from water splitting was designed to overcome the problems caused by gas diffusion and mixing of multiple products in the traditional hydrogen production processes.In the microgravity environment，hydrogen is difficult to desorb and transport quickly on the electrode surface，which significantly affects the reaction efficiency.The functional interface prepared in this study allows the gas to penetrate rapidly in the direction of gravity，providing an effective solution to overcome the challenges of gas desorption and separation on the interface of multi-phase reaction in the extraterrestrial environment.This study developed a functional device for extraterrestrial hydrogen production by preparing a composite catalyst with excellent catalytic performance and a biomimetic functional interface adapted to the microgravity environment.It not only suggests theoretical and experimental basis for the utilization of extraterrestrial in-situ resources，but also supports a solution for the design of hydrogen evolution reaction device in the construction of extraterrestrial carbon-hydrogen-oxygen closed material system.

Key words: hydrogen production by electrolysis of water, catalyst, microgravity, bubbles, gas-liquid separation interface