Photocatalytic Water Splitting: Carrier Diffusion-Reaction (2D)

This 2D companion replaces the 3D version's particle-race animation with the actual physics underneath it: a finite-difference solver advancing the coupled electron and hole reaction-diffusion equations across the photocatalyst particle's cross-section, frame by frame, in real time. Photogeneration switches on only when the photon energy clears the bandgap; the two density fields then diffuse, annihilate wherever they overlap at a rate set by the recombination slider, and lose population at the particle's edge through a surface-capture term that only counts as chemistry when the band-edge alignment thermodynamically allows it. The apparent quantum yield, and the H₂ and O₂ evolution rates, are read directly off the integrated field — not sampled from individual-particle odds — giving an independent, continuum-physics cross-check on why band-edge position (not just bandgap size) decides whether a material can split water at all.