Dual-Terminal Engineering of Nanorod Heterojunctions Enables Charge-Proton Balanced Photocatalytic H2 Evolution Coupled with Imine Production

Abstract Light-driven conversion of primary amines to imines and H2 offers a compelling carbon-neutral route to the co-production of high-value fine chemicals and clean fuels, yet its efficiency remains constrained by an asymmetric imbalance in the supply and consumption of charges and protons. Here, we present a dual-terminal engineering strategy for heterojunction photocatalysts that circumvents this challenge by concurrently modulating CdS nanorod length at the oxidation terminus for C−N coupling of benzylamine (BA) into N-benzylidenebenzylamine (BBA), while tailoring Ag species at the reduction terminus for H2 generation. Spectroscopic and theoretical investigations untangle that elongating the nanorod length enhances intrinsic electron-hole separation within CdS and promotes interfacial electron transfer from CdS to the Ag species, whereas distinct Ag species (Ag and Ag2S) exhibit markedly different electron-trapping and H2-evolution capabilities. Specifically, the faster electron acceptance yet slower H2 evolution kinetics of Ag drive the accumulation of unconsumed electrons and protons, which are diverted toward BBA hydrogenation to secondary amines—simultaneously retarding further BA dehydrogenation and accelerating CdS photocorrosion through the buildup of unreacted holes. Conversely, Ag2S achieves kinetic harmony between electron trapping and H2 evolution, effectively suppressing both parasitic reactions and photocorrosion. Consequently, Ag2S/CdS nanorods of optimal length deliver near-stoichiometric and long-sustained co-evolution of BBA and H2 at outputs of 38.9 and 35.0 mmol gcat−1 h−1, together with 100% BBA selectivity. This work opens a generalizable avenue for orchestrating charge and proton equilibrium in heterojunction photocatalysts toward efficient and selective redox transformations.