An experimental and modeling/simulation-based evaluation of the efficiency and operational performance characteristics of an integrated, membrane-free, neutral pH solar-driven water-splitting system

摘要: The efficiency limits, gas-crossover behavior, formation of local pH gradients near the electrode surfaces, and safety characteristics have been evaluated experimentally as well by use multi-physics modeling simulation methods for an integrated solar-driven water-splitting system that operates with bulk electrolyte solutions buffered at near-neutral pH. membrane-free utilized a triple-junction amorphous hydrogenated Si (a-Si:H) cell light absorber, Pt cobalt phosphate (Co–Pi) electrocatalysts hydrogen-evolution reaction (HER) oxygen-evolution (OER), respectively, aqueous solution = 9.2 1.0 M boric acid/borate electrolyte. Although solar-to-electrical stand-alone a-Si:H photovoltaic was 7.7%, solar-to-hydrogen (STH) conversion limited under steady-state operation to 3.2%, surfaces accounted largest voltage loss. exhibited negligible product-recombination loss while operating current densities 3.0 mA cm−2, but significant crossover products (up 40% H2 in O2 chamber), indicating not intrinsically safe. A contained membrane minimize gas crossover, which otherwise identical system, yielded very low energy-conversion efficiencies steady state, due transference numbers protons across membranes resulting electrodialysis consequent large concentration both buffer counterions surfaces. results showed despite addition buffering agent solution, during developed electrodes. Hence, although pH, experienced environments were either highly acidic or alkaline nature, changing chemical form exposing electrodes potentially corrosive conditions. In gradients, STH types systems mass transport ionic species Even <3 drops these exceeded combined electrocatalyst overpotentials hydrogen- reactions 10 cm−2. such fundamentally and/or co-evolved explosive mixtures H2(g) O2(g) presence active catalysts recombination O2(g).