Simultaneous requirement of excellent interface passivation and low thermal budget is a desirable feature for low cost Si based carrier selective solar cells. Accordingly, Titanium dioxide (TiO2), a widely used electron selective material, finds challenges related to thermal annealing like phase change and compatibility with thermal budget of hole transport layers. To address this, here we report a H-2 plasma treatment process at room temperature which significantly reduces the surface recombination velocity (similar to 40 cm/s). Consequently, the reverse saturation current of the Si-TiO2 diode improves by a factor of 40, built-in potential improves by 100 mV, and the diode exhibits a near unity ideality factor. Using the same method, our Si-based double heterojunction solar cell results in an absolute increase of 2.4% in efficiency over devices with conventional thermal annealing. Given the ease of implementation and excellent performance, the proposed method is a promising alternative to thermal annealing for Si based heterojunction devices.