Electrochemical germane (GeH4) synthesis via dual-descriptor screening and integrated theoretical-experimental validation

Abstract

Electrochemical synthesis of germane (GeH₄) from GeO₂ represents a safe and sustainable alternative to conventional thermal methods that suffer from high production costs and excessive byproducts. However, the eight proton-electron transfer steps involve multiple intermediates and competing side reactions, rendering the reaction mechanism highly complex. Herein, a comprehensive reaction network encompassing dissociative and associative mechanisms (D-T, D-H, A-T, and A-H) was systematically established and analysed. Descriptor screening based on density functional theory (DFT) identified *Ge and *GeH adsorption free energies, G_ad(Ge) and G_ad(GeH), as robust dual descriptors through strong linear scaling relationships with key intermediates. Thermodynamic mapping revealed that non-hydrolysis associative pathways, particularly the A-T mechanism, are most favorable within a moderate adsorption window. Copper (Cu) emerged as the optimal catalyst, balancing hydrogen activation and Ge–H bond formation with a low theoretical limiting potential (0.71 V). Experimental validation confirmed that Cu exhibits superior activity and selectivity compared to Bi and Ni, consistent with descriptor-based predictions. Kinetic analysis on the Cu(111) surface further determined *Ge → *GeH hydrogenation as the rate-determining step in the less favorable pathway, with a free-energy barrier of 0.95 eV, directly linking the dual descriptors to kinetic constraints. This integrated framework provides mechanistic insights and descriptor-driven guidance for the rational design of selective GeH₄ electrocatalysts, and establishing a generalizable paradigm for the sustainable electrochemical synthesis of electronic specialty gases.